adrenomedullin and Pheochromocytoma

Adrenomedullin (AM) is a recently discovered potent vasodilatory peptide, originally isolated in extracts of human pheochromocytoma, with activities including maintenance of cardiovascular and renal homeostasis through vasodilatation, diuresis and natriuresis. Human AM consists of 52 amino acids with a 6-member ring structure linked by a disulfide bond and amidated COOH terminal, which belongs to calcitonin gene-related peptide (CGRP) and amylin. The main sites of AM production are the lungs, vascular tissues (both endothelial and smooth muscle cells), heart, kidney, adrenal glands, pancreatic islets, placenta, anterior pituitary gland and gastrointestinal neuroendocrine system. Intravenous injection of AM increases blood flow predominantly in the tissues with the highest AM expression, suggesting that AM functions primarily as a paracrine/autocrine hormone, but it is also important as circulating hormone. The objective of this review is to analyze the evidence that AM may play a role in some endocrine disorders.

Topics: Adrenal Insufficiency; Adrenocorticotropic Hormone; Adrenomedullin; Amino Acid Sequence; Cushing Syndrome; Diabetes Mellitus; Endocrine System Diseases; Female; Humans; Hyperaldosteronism; Hyperparathyroidism; Hyperthyroidism; Insulinoma; Male; Menstrual Cycle; Molecular Sequence Data; Molecular Structure; Paraneoplastic Endocrine Syndromes; Peptides; Pheochromocytoma; Pregnancy

In the last several decades, the concept of "endocrinology" has been greatly changed. One major change was due to the discovery of peptide hormones secreted by the organs that were not "classical" endocrine organs. For example, corticotropin-releasing hormone and many neuropeptides are secreted by the neurons, atrial natriuretic peptide by the heart, endothelin-1 by the vascular endothelial cells, and leptin by the adipose tissues. Now, the brain, heart, vascular tissue and adipose tissue can be considered to be endocrine organs. Cardiovascular diseases and obesity are therefore important targets of the endocrine research. Adrenomedullin is a potent vasodilator peptide consisting of 52 amino acids. It was originally discovered from a human pheochromocytoma, and belongs to the calcitonin gene-related peptide (CGRP) family. Adrenomedullin is produced and secreted by various types of cells, for example, vascular endothelial and smooth muscle cells, cardiomyocytes, fibroblasts, macrophages, neurons, glial cells, and retinal pigment epithelial cells. Such ubiquitous expression has not been observed in other neuropeptides, including neuropeptide Y and CGRP. Expression of adrenomedullin is induced by hypoxia and proinflammatory cytokines. In addition to vasodilator actions, this peptide has central inhibitory actions on water drinking and salt appetite, effects on the secretion of some hormones and cytokines, inotropic actions and effects on cell growth and apoptosis. Adrenomedullin is produced by various non-endocrine tumors, as well as endocrine tumors, and acts as a growth stimulatory factor for the tumor cells. Adrenomedullin seems to be involved in the pathophysiology of many diseases, including ischemic heart diseases, inflammatory diseases, tumors, and even eye diseases. The adrenomedullin research implies that "the neuroendocrine system" exists in much broader types of cells than previously thought, and that the endocrine research is able to contribute to the understanding of the pathophysiology of many diseases.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Amino Acid Sequence; Animals; Endocrinology; Eye; Humans; Molecular Sequence Data; Peptides; Pheochromocytoma

Adrenomedullin (AM) is a vasodilator peptide first identified in pheochromocytoma tissue, but endothelial cells and vascular smooth muscle cells actively secrete AM in addition to expressing AM receptors. AM dilates blood vessels through its direct action on the smooth muscle and the endothelial cell-mediated nitric oxide pathway. We have further demonstrated that AM is synthesized and secreted from macrophages, fibroblasts, cardiomyocytes and many other types of cells. AM secretion from these cells as well as the vascular wall cells are commonly stimulated with inflammatory cytokines and lipopolysaccharide. AM receptor is also widely distributed, and AM is shown to regulate production of inflammatory cytokines and cell growth. Based on these data, AM is deduced to be a multi-functional peptide participating in the regulation of vascular tone, inflammation and other physiologic events of the vasculature.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Amino Acid Sequence; Animals; Blood Pressure; Cell Division; Cytokines; Endothelium, Vascular; Fibroblasts; Humans; Inflammation; Lipopolysaccharides; Mice; Mice, Transgenic; Molecular Sequence Data; Muscle, Smooth, Vascular; Neoplasm Proteins; Nitric Oxide; Organ Specificity; Peptides; Pheochromocytoma; Rats; Receptors, Adrenomedullin; Receptors, Peptide; Shock, Septic; Vasodilation

Adrenomedullin (ADM) is a recently discovered peptide with potent vasorelaxing and natriuretic properties originally isolated from human pheochromocytoma. Adrenomedullin has been reported to be present in normal adrenal medulla, heart, lung and kidney as well as in plasma and urine. ADM shares some structural homology with calcitonin gene related peptide (CGRP). ADM acts on target cells through its unique receptors and CGRP1 receptors. In both cases cyclic AMP seems to be the main second messenger. ADM may function as a circulating hormone and as an autocrine/paracrine mediator involved in the regulation of cardiovascular system and renal function. Plasma concentration of ADM is elevated in patients with congestive heart failure, arterial hypertension, pulmonary hypertension, renal failure and sepsis suggesting its role in pathophysiology of these disorders. Recently another product od adrenomedullin gene, proadrenomedullin N-terminal 20-peptide (PAMP) has been described. This peptide has also vasodilating activity resulting from its inhibitory action on norepinephrine release from sympathetic endings and adrenal medulla.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Animals; Cardiovascular Diseases; Cardiovascular Physiological Phenomena; Cyclic AMP; Humans; Kidney; Membrane Proteins; Peptides; Pheochromocytoma; Receptors, Adrenomedullin; Receptors, Peptide

Although approximately 90% of patients diagnosed with hypertension have essential hypertension, it is important that secondary hypertension is considered; diagnosed, when present; and managed either medically or surgically. Although the most common organ involved in the etiology of secondary hypertension is the kidney, disorders of the adrenal gland also play a major role. This review focuses on recent findings and controversies about the adrenal medulla and, where appropriate, on the role of the adrenal medulla in hypertension.

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adrenomedullin; Animals; Humans; Hypertension; Peptides; Pheochromocytoma; Vasodilation

Despite adequate presurgical management, blood pressure fluctuations are common during resection of pheochromocytoma or sympathetic paraganglioma (PPGL). To a large extent, the variability in blood pressure control during PPGL resection remains unexplained. Adrenomedullin and B-type natriuretic peptide, measured as MR-proADM and NT-proBNP, respectively, are circulating biomarkers of cardiovascular dysfunction. We investigated whether plasma levels of MR-proADM and NT-proBNP are associated with blood pressure fluctuations during PPGL resection.. Study subjects participated in PRESCRIPT, a randomized controlled trial in patients undergoing PPGL resection. MR-proADM and NT-proBNP were determined in a single plasma sample drawn before surgery. Multivariable linear and logistic regression analyses were used to explore associations between these biomarkers and blood pressure fluctuations, use of vasoconstrictive agents during surgery as well as the occurrence of perioperative cardiovascular events.. A total of 126 PPGL patients were included. Median plasma concentrations of MR-proADM and NT-proBNP were 0.51 (0.41-0.63) nmol/L and 68.7 (27.9-150.4) ng/L, respectively. Neither MR-proADM nor NT-proBNP were associated with blood pressure fluctuations. There was a positive correlation between MR-proADM concentration and the cumulative dose of vasoconstrictive agents (03B2 0.44, P =0.001). Both MR-proADM and NT-proBNP were significantly associated with perioperative cardiovascular events (OR: 5.46, P =0.013 and OR: 1.54, P =0.017, respectively).. plasma MR-proADM or NT-proBNP should not be considered as biomarkers for the presurgical risk assessment of blood pressure fluctuations during PPGL resection. Future studies are needed to explore the potential influence of these biomarkers on the intraoperative requirement of vasoconstrictive agents and the perioperative cardiovascular risk.

Topics: Adrenal Gland Neoplasms; Adrenergic Antagonists; Adrenomedullin; Adult; Aged; Biomarkers; Blood Pressure; Cardiovascular Diseases; Cross-Sectional Studies; Female; Follow-Up Studies; Heart Failure; Humans; Intraoperative Complications; Male; Middle Aged; Natriuretic Peptide, Brain; Pheochromocytoma; Prognosis; Risk Assessment; Treatment Outcome

The hypotensive peptide adrenomedullin was first isolated in extracts of human pheochromocytoma. There is, however, no information available on the behaviour of circulating adrenomedullin or on the correlation with catecholamines in patients with pheochromocytoma.. 1) to investigate whether plasma adrenomedullin levels were changed in 10 patients with pheochromocytoma when compared to 21 healthy subjects and 16 patients with essential hypertension; 2) to determine whether or not adrenomedullin has a counter-regulatory role in catecholamine excess in pheochromocytoma or is responsible for hemodynamic modifications before and after tumour resection; 3) to determine tissue distribution of iradrenomedullin in the pheochromocytoma.. Plasma adrenomedullin and catecholamine levels were measured in all patients with pheochromocytoma before and four weeks after tumour removal. In the four patients undergoing resection of tumours, plasma levels of adrenomedullin were measured at different time-points during surgery.. The mean plasma adrenomedullin concentrations ( SD) in patients with pheochromocytoma (37.9 +/- 6pg/ml) were significantly higher (p<0.0001) than those in normal subjects (13.7 +/- 6.1 pg/mI) and patients with essential hypertension (22.5 +/- 9.lpg/ml). Adrenomedullin levels correlated with plasma noradrenaline (r = 0.516, p = 0.0124). In all patients with pheochromocytoma, plasma adrenomedullin concentrations decreased after removal of tumours (from 37.9 +/- 6 to 10.9 +/- 4.6 pg/ml; p < 0.0001). In the four patients studied during surgery, baseline plasma adrenomedullin and noradrenaline levels were markedly elevated, and increased significantly with tumour manipulation, decreasing 24 hours after operation. Adrenal medulla cells surrounding the pheochromocytoma site stained for ir-adrenomedullin, whereas only isolated cells of pheochromocytoma stained for the peptide.. This study demonstrates that circulating adrenomedullin is increased in pheochromocytoma, and is also correlated with plasma noradrenaline levels. Adrenomedullin may represent an additional biochemical parameter for clinical monitoring of patients with pheochromocytoma.

Topics: Adrenal Gland Neoplasms; Adrenalectomy; Adrenomedullin; Adult; Catecholamines; Female; Hemodynamics; Humans; Hypertension; Immunohistochemistry; Male; Middle Aged; Norepinephrine; Peptides; Pheochromocytoma; Treatment Outcome

Adrenomedullin is a novel hypotensive peptide, newly discovered in pheochromocytoma. Because immunoreactive adrenomedullin is present in human plasma, adrenomedullin may play a role in regulating blood pressure. A recent report showed that human adrenomedullin mRNA is expressed not only in pheochromocytoma but also in the normal adrenal medulla, kidney, lung, and ventricle. However, whether or not these organs actually release adrenomedullin into the circulation remains unknown. To investigate the sites of production and degradation of adrenomedullin in human subjects, we obtained blood samples from various sites and measured immunoreactive adrenomedullin concentrations. In study 1, blood samples were obtained from the infrarenal inferior vena cava, suprarenal inferior vena cava, superior vena cava, right atrium, right ventricle, pulmonary artery, pulmonary capillary, left ventricle, and aorta during cardiac catheterization in 15 patients with ischemic heart disease (67 +/- 10 years). In study 2, blood samples were taken from the infrarenal inferior vena cava, suprarenal inferior vena cava, right and left renal veins, and left adrenal vein in 5 hypertensive patients (42 +/- 14 years) suspected of having renovascular hypertension. In study 3, peripheral venous blood samples were obtained in 2 patients (males, 45 and 36 years old) with pheochromocytoma at rest and during hypertensive attacks. Plasma adrenomedullin concentrations were measured by a newly developed radioimmunoassay. In study 1, there were no significant differences in plasma adrenomedullin concentrations in various sites of the right-side circulation. There was no step-up of plasma adrenomedullin levels in the coronary sinus. However, the plasma concentration of adrenomedullin in aorta was slightly but significantly lower than in pulmonary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adrenomedullin; Adult; Aged; Antihypertensive Agents; Blood Pressure; Epinephrine; Female; Gene Expression; Heart Rate; Heart Ventricles; Humans; Hypertension; Kidney; Lung; Male; Metabolic Clearance Rate; Middle Aged; Myocardial Ischemia; Myocardium; Norepinephrine; Peptide Biosynthesis; Peptides; Pheochromocytoma; Pulmonary Artery; Pulmonary Circulation; RNA, Messenger

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Amino Acid Sequence; Animals; Blood Platelets; Blood Pressure; Calcitonin Gene-Related Peptide; Cyclic AMP; History, 20th Century; Humans; Hypotension; Molecular Sequence Data; Pheochromocytoma; Rats

Pheochromocytomas are catecholamine-producing tumors which are generally benign, but which can also present as or develop into malignancy. Molecular pathways of malignant transformation remain poorly understood. Pheochromocytomas express various trophic peptides which may influence tumoral cell behavior. Here, we investigated the expression of trophic amidated peptides, including pituitary adenylate cyclase-activating polypeptide (PACAP), neuropeptide Y (NPY), and adrenomedullin (AM), and their receptors in benign and malignant pheochromocytomas in order to assess their potential role in chromaffin cell tumorigenesis and malignant transformation. PACAP, NPY, and AM are expressed in the majority of pheochromocytomas studied; NPY exhibiting the highest mRNA levels relative to reference genes. Although median gene expression or peptide levels were systematically lower in malignant compared to benign tumors, no statistically significant difference was found. Among all the receptors of these peptides that were analyzed, only the AM receptor RDC1 displayed a differential expression between benign and malignant pheochromocytomas. This receptor exhibited a fourfold higher expression in malignant than in benign tumors. AM and stromal cell-derived factor 1, which has also been described as a ligand for RDC1, increased the number of human pheochromocytoma cells in primary culture and exerted anti-apoptotic activity on rat pheochromocytoma PC12 cells. In addition, RDC1 gene silencing decreased the number of viable PC12 cells. This study shows the expression of several trophic peptides and their receptors in benign and malignant pheochromocytomas, and suggests that AM and its RDC1 receptor could be involved in chromaffin cell tumorigenesis through pro-survival effects. Therefore, AM and RDC1 may represent valuable targets for the treatment of malignant pheochromocytomas.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Animals; Blotting, Western; Cell Survival; Formazans; Gene Expression Regulation, Neoplastic; Humans; Immunohistochemistry; Neuropeptide Y; PC12 Cells; Pheochromocytoma; Pituitary Adenylate Cyclase-Activating Polypeptide; Rats; Receptors, Adrenomedullin; Receptors, Neuropeptide Y; Receptors, Peptide; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Tetrazolium Salts

A 45-year-old man on long-term hemodialysis (HD) was incidentally discovered to have a pheochromocytoma and underwent successful resection. This patient was normotensive, and had no symptoms suggesting pheochromocytoma. The plasma concentrations of total adrenomedullin (AM-T) and mature AM (AM-m) were higher than those in normal controls. To elucidate the source of AM, we measured plasma AM levels by immunoradiometric assay before and 3 weeks after surgery in addition to plasma adrenaline, noradrenaline and dopamine. AM expression was also assessed by immunoblot and immunohistochemical analyses on normal adrenal and tumor tissues. After surgery, elevated plasma adrenaline levels returned to the normal range; however, the levels of AM-T and AM-m remained almost the same as the preoperative values. Furthermore, although AM was expressed in both normal adrenal and tumor tissues, the AM expression level was less in tumor. In this case, it was suggested that elevation in plasma AM level might be a factor associated with normotensive blood pressure; however, adrenal pheochromocytoma was not a major source of circulating AM. To our knowledge, this is the first case of pheochromocytoma in patient with HD associated with AM in the literature.

Topics: Adrenal Gland Neoplasms; Adrenalectomy; Adrenomedullin; Biomarkers, Tumor; Calcitonin Gene-Related Peptide; Humans; Immunoblotting; Immunoradiometric Assay; Kidney Failure, Chronic; Male; Middle Aged; Peptides; Pheochromocytoma; Postoperative Period; Prognosis; Renal Dialysis

This study investigates the expression of human adrenomedullin (ADM) and its receptor-receptor activity modifying protein 2/calcitonin receptor-like receptor (RAMP2/CRLR) mRNA in pheochromocytoma by reverse transcriptase polymerase chain reaction (RT-PCR) and its effect on the proliferation of pheochromocytoma cells by MTT. The mRNA expression of ADM and its receptor RAMP2/CRLR was present in normal adrenal medulla and pheochromocytoma tissues. The mRNA expression of ADM, RAMP2, and CRLR is markedly higher in pheochromocytomas than in normal medulla. ADM inhibits the proliferation of human pheochromocytoma cells and exerts a possible autocrine or paracrine effect in the adrenal.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Adult; Base Sequence; Calcitonin Receptor-Like Protein; DNA Primers; Female; Humans; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Middle Aged; Pheochromocytoma; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Proteins; Receptors, Calcitonin; RNA, Messenger

To investigate the expression of human adrenomedullin (ADM) and its receptor-receptor activity modifying protein 2/calcitonin receptor-like receptor (RAMP2/CRLR) mRNA in the tissues of normal adrenal medulla and pheochromocytoma.. Total RNA was extracted from normal adrenal medulla and pheochromocytomas. The expression of ADM and RAMP2/CRLR mRNA were studied by reverse transcription-polymerase chain reaction. The ratios of ADM/GAPDH, RAMP2/ GAPDH, CRLR/GAPDH were used to evaluate the expression levels of ADM, RAMP2 and CRLR mRNA.. Expressions of ADM and its receptor- RAMP2/CRLR mRNA were detected in normal adrenal medulla and pheochromocytoma tissues. ADM/GAPDH were 0.48+/-0.09 and 0.75+/-0.24, RAMP2/ GAPDH 0.79+/-0.12 and 1.29+/-0.30, CRLR/GAPDH 0.40+/-0.08 and 0.87+/-0.22 in normal adrenal medulla and pheochromocytomas, respectively (P < 0.05).. ADM exerts a possible autocrine or paracrine effect in the adrenal. ADM may be involved in the pathogenesis of pheochromocytoma.

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adrenomedullin; Adult; Calcitonin Gene-Related Peptide; Female; Humans; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; Middle Aged; Peptides; Pheochromocytoma; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Proteins; Receptors, Adrenomedullin; Receptors, Calcitonin; Receptors, Peptide; RNA, Messenger

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are multi-functional peptides derived from the same precursor, proadrenomedullin. We have studied the regulatory mechanism of expression of these peptides during neuronal differentiation of rat pheochromocytoma PC12 cells by nerve growth factor (NGF). The cellular levels of the peptides increased slightly, and then progressively decreased below the control by NGF. Immunoreactive (ir)-AM in the medium was transiently increased by NGF. Cytochemical staining showed that ir-AM and ir-PAMP were abundantly present in cytoplasm in the undifferentiated cells, and were decreased during culture with NGF. There was no preferential localization of ir-AM or ir-PAMP in neurites in comparison with in cytoplasm in the differentiated cells. Northern blot analysis showed that mRNA encoding these peptides, as detected as a band of 1.6 kb, increased more than three-fold at 1 h after the addition of NGF and then progressively decreased to one fifth of the control during 72 h. Degradation rate of the mRNA was slowed by NGF even when mRNA level is decreased after 72 h of NGF treatment. The transcription rate of their gene increased transiently and then decreased by the long-term treatment with NGF. These results demonstrate that expression of AM and PAMP is regulated by NGF along with time-dependent differentiation: AM gene transcription is transiently activated by NGF, whereas it was suppressed during neuronal differentiation of the cells.

Topics: Adrenomedullin; Animals; Blotting, Northern; Cell Differentiation; Gene Expression Regulation; Immunohistochemistry; Nerve Growth Factor; Neurons; PC12 Cells; Peptide Biosynthesis; Peptide Fragments; Peptides; Pheochromocytoma; Protein Biosynthesis; Protein Precursors; Proteins; Radioimmunoassay; Rats; RNA, Messenger; Time Factors; Transcription, Genetic

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Animals; Antihypertensive Agents; Hemodynamics; Humans; Hypertension, Pulmonary; Peptides; Pheochromocytoma; Pulmonary Circulation

Urotensin II is a potent vasoactive peptide, which was originally isolated from fish urophysis. We studied expression of urotensin II and its receptor mRNAs in the tumor tissues of adrenocortical tumors, pheochromocytomas and neuroblastomas. Effects of exogenously added urotensin II on cell proliferation were studied in a human adrenocortical carcinoma cell line, SW-13 and a human renal cell carcinoma cell line, VMRC-RCW. The reverse transcriptase polymerase chain reaction (RT-PCR) showed expression of urotensin II and its receptor mRNAs in all the samples examined; seven pheochromocytomas, nine adrenocortical adenomas (four with primary aldosteronism, four with Cushing syndrome and one with non-functioning adenoma), four adrenocortical carcinomas, one ganglioneuroblastoma and five neuroblastomas, as well as four normal portions of adrenal glands (cortex and medulla). Urotensin II-like immunoreactivity was detected in one of eight adrenocortical adenomas, two of four adrenocortical carcinomas, one of six pheochromocytomas, and one of five neuroblastomas by radioimmunoassay, but not in normal portions of adrenal glands (detection limit; 0.2pmol/g wet weight). Treatment with urotensin II for 24h significantly increased number of SW-13 cells (at 10(-8) and 10(-7)mol/l) and VMRC-RCW cells (at 10(-8)mol/l). These findings raise the possibility that urotensin II may act as an autocrine/paracrine growth stimulating factor in adrenal tumors.

Topics: Adrenal Cortex Neoplasms; Adrenocortical Carcinoma; Adrenomedullin; Cell Division; Gene Expression Regulation, Neoplastic; Humans; Neuroblastoma; Peptides; Pheochromocytoma; Radioimmunoassay; Receptors, G-Protein-Coupled; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured; Urotensins

Adrenomedullin (ADM) is a hypotensive peptide isolated from human pheochromocytoma tissue. In order to identify the pathophysiological effects of ADM on the etiology of adrenal diseases which can induce hypertension, the localization of immunoreactive adrenomedullin (ir-ADM) in adrenal tissue of subjects with normal adrenal and patients with different adrenal diseases was investigated by means of immunohistochemical staining.. Peroxidase anti-peroxidase complex method was undertaken in the tissue of human adrenal cortex (n = 10) and medulla (n = 10)of subjects with normal adrenal, as well as in the tissue of pheochromocytoma (n = 31), primary aldosteronism including adrenocortical adenoma (n = 13) and hyperplasia (n = 9), Cushing's syndrome including adrenocortical adenoma (n = 12), hyperplasia (n = 10), carcinoma (n = 4) and non-functional adrenocortical carcinoma (n = 7).. Positive immunohistochemical staining of ir-ADM was observed in all the cases of normal adrenal medulla and 16 of the 31 cases of pheochromocytoma. The intensity of immunohistochemical staining of ir-ADM in the majority of pheochromocytoma was lower than that in normal adrenal medulla (P < 0.01). The number of pheochromocytoma cases with positive staining in paroxysmal hypertensive group was higher than that in sustained hypertensive group (P < 0.05). Negative immunohistochemical staining was found in all the cases of normal human adrenal cortex, adrenocortical adenoma, hyperplasia and carcinoma.. It is suggested that heterogeneous of localization of ir-ADM in pheochromocytoma tissue may be correlated to the diversity of blood pressure in patients with pheochromocytoma. The pathophysiological effects of ADM on the etiology of pheochromocytoma should be further investigated.

Topics: Adrenal Cortex; Adrenal Gland Diseases; Adrenal Medulla; Adrenomedullin; Humans; Immunohistochemistry; Peptides; Pheochromocytoma

Controversy exists as to the origin of plasma adrenomedullin (AM). To elucidate the source of plasma AM, we measured two molecular forms of AM, an active form of mature AM (AM-m) and an intermediate inactive form of glycine-extended AM (AM-Gly), by immunoradiometric assay using specific kits in two female patients with pheochromocytoma before and 3 weeks after surgery. We also measured plasma AM-m, AM-Gly, and AM-T (AM-m + AM-Gly) levels, in addition to plasma epinephrine (E) and norepinephrine (NE) levels, in bilateral adrenal veins of one patient. Although plasma E and NE levels decreased markedly after surgery in these patients, changes in plasma AM appeared to be confined to the normal range. There were no obvious differences in plasma AM-T, AM-m, or AM-Gly levels in adrenal veins between healthy tissue and tumor sides. Furthermore, plasma AM-T, AM-m, or AM-Gly levels in adrenal veins were comparable with those in the infrarenal inferior vena cavae (IVC) or the suprarenal IVC. In contrast, plasma E and NE levels increased in the adrenal vein of the healthy side and increased further in the adrenal vein of the tumor side compared with those in the infrarenal IVC. These results suggest that the origin of plasma E and NE is the adrenal gland and that elevated plasma levels of E and NE in pheochromocytoma are due to excessive production of E and NE in the adrenal gland of the tumor side. In contrast, it is suggested that neither plasma AM levels in the adrenal vein of the healthy side nor those of the tumor side contribute to the systemic levels of plasma AM. The present results appear to be consistent with the hypothesis that the source of circulating AM is systemic vasculature.

Topics: Adolescent; Adrenomedullin; Calcitonin Gene-Related Peptide; Epinephrine; Female; Humans; Middle Aged; Norepinephrine; Peptides; Pheochromocytoma; Radioimmunoassay

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Eye; Humans; Peptides; Pheochromocytoma; Vasodilator Agents

Proadrenomedullin N-terminal 20 peptide (PAMP-[1-20]; ARLDVASEFRKKWNKWALSR-amide) is a potent hypotensive and catecholamine release-inhibitory peptide released from chromaffin cells. We studied the mechanism of PAMP action and how its function is linked to structure. We tested human PAMP-[1-20] on catecholamine secretion in PC12 pheochromocytoma cells and found it to be a potent, dose-dependent (IC50 approximately 350 nmol/L) secretory inhibitor. Inhibition was specific for nicotinic cholinergic stimulation since PAMP-[1-20] failed to inhibit release by agents that bypass the nicotinic receptor. Nicotinic cationic (22Na+,45Ca2+) signal transduction was disrupted by this peptide, and potencies for inhibition of 22Na+ uptake and catecholamine secretion were comparable. Even high-dose nicotine failed to overcome the inhibition, suggesting noncompetitive nicotinic antagonism. N- and C-terminal PAMP truncation peptides indicated a role for the C-terminal amide and refined the minimal active region to the C-terminal 8 amino acids (WNKWALSR-amide), a region likely to be alpha-helical. PAMP also blocked (EC50 approximately 270 nmol/L) nicotinic cholinergic agonist desensitization of catecholamine release, as well as desensitization of nicotinic signal transduction (22Na+ uptake). Thus, PAMP may exert both inhibitory and facilitatory effects on nicotinic signaling, depending on the prior state of nicotinic stimulation. PAMP may therefore contribute to a novel, autocrine, homeostatic (negative-feedback) mechanism controlling catecholamine release.

Topics: Adrenomedullin; Animals; Calcium; Catecholamines; Cell Line; Humans; Nicotine; Nicotinic Agonists; Nicotinic Antagonists; Peptide Fragments; Peptides; Pheochromocytoma; Proteins; Rats; Signal Transduction; Sodium; Structure-Activity Relationship; Tumor Cells, Cultured; Vasodilator Agents

Adrenomedullin is a potent vasodilator peptide that was isolated from human pheochromocytoma. We developed a sensitive and specific radioimmunoassay for adrenomedullin and studied the presence of adrenomedullin in human adrenal glands and adrenal tumors, including pheochromocytoma. High concentrations of immunoreactive adrenomedullin were found in normal parts of adrenal glands (cortex and medulla) (12.6 +/- 1.0 pmol/g wet wt, N = 7, mean +/- SEM). High concentrations of immunoreactive adrenomedullin were also present in the tumor tissues of pheochromocytoma (4.5 +/- 1.5 pmol/g wet wt, N = 11). Immunoreactive adrenomedullin was detected in some adrenocortical tumors, but these concentrations were much lower than those in the normal adrenal glands and pheochromocytomas. Reverse phase high-performance liquid chromatography of the normal adrenal gland and pheochromocytoma showed a peak eluting in the position of synthetic adrenomedullin 1-52. The present study has shown the presence of high concentrations of immunoreactive adrenomedullin in the normal adrenal glands and pheochromocytomas.

Topics: Adenocarcinoma; Adenoma; Adrenal Cortex Neoplasms; Adrenal Gland Neoplasms; Adrenal Glands; Adrenomedullin; Humans; Peptides; Pheochromocytoma; Radioimmunoassay

Adrenomedullin is a potent vasorelaxant/hypotensive peptide recently isolated from human pheochromocytoma. We demonstrate here a novel role of this peptide as an apoptosis survival factor for rat endothelial cells. When rendered quiescent by serum deprivation, a fraction of endothelial cell cultures showed morphological and biochemical features characteristic of apoptosis. Adrenomedullin significantly suppressed apoptosis without inducing cell proliferation. Rat endothelial cells that contained high affinity binding sites for adrenomedullin expressed adrenomedullin gene and released the peptide into culture media. Addition of preimmune rabbit serum prevented apoptosis, whereas rabbit antiadrenomedullin antiserum partially, but significantly, abrogated the protective effect of the preimmune serum, suggesting its autocrine/paracrine role. Although adrenomedullin induced intracellular cAMP formation, other cAMP-elevating agonists, such as prostaglandin I2 and forskolin, did not affect apoptosis. Furthermore, adenosine 3',5'-cyclicmonophosphothioate Rp-isomer, a cAMP antagonist, did not block the cell survival effect of adrenomedullin. Adrenomedullin neither increased intracellular Ca2+ concentrations nor inositol-1,4,5-trisphosphate levels in rat endothelial cells. These results demonstrate that adrenomedullin suppresses serum deprivation-induced apoptosis of rat endothelial cells via cAMP-independent mechanism.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Animals; Aorta; Apoptosis; Cell Division; Cell Survival; Cells, Cultured; Colforsin; Cyclic AMP; DNA; Endothelium, Vascular; Epoprostenol; Humans; Immune Sera; Kinetics; Male; Membrane Proteins; Peptides; Pheochromocytoma; Rabbits; Rats; Rats, Wistar; Receptors, Adrenomedullin; Receptors, Peptide; Thionucleotides; Vasodilator Agents

Adrenomedullin (ADM) is a polypeptide originally discovered in a human pheochromocytoma and is also present in normal adrenal medulla. It has been proposed that ADM could be involved in the regulation of adrenal steroidogenesis via paracrine mechanisms. Our aim was to find out if ADM gene is expressed in adrenocortical tumors and how ADM gene expression is regulated in adrenal cells. ADM mRNA was detectable by Northern blotting in most normal and hyperplastic adrenals, adenomas and carcinomas. The average concentration of ADM mRNA in the hormonally active adrenocortical adenomas was about 80% and 7% of that in normal adrenal glands and separated adrenal medulla respectively. In adrenocortical carcinomas, the ADM mRNA concentration was very variable, but on average it was about six times greater than that in normal adrenal glands. In pheochromocytomas, ADM mRNA expression was about ten times greater than that in normal adrenals and three times greater than in separated adrenal medulla. In primary cultures of normal adrenal cells, a protein kinase C inhibitor, staurosporine, reduced ADM mRNA accumulation in a dose- and time-dependent fashion (P < 0.01), whereas it simultaneously increased the expression of human cholesterol side-chain cleavage enzyme (P450 scc) gene (a key gene in steroidogenesis). In cultured Cushing's adenoma cells, adrenocorticotropin, dibutyryl cAMP ((Bu)2cAMP) and staurosporine inhibited the accumulation of ADM mRNA by 40, 50 and 70% respectively (P < 0.05), whereas the protein kinase C activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA), increased it by 50% (P < 0.05). In primary cultures of pheochromocytoma cells, treatment with (Bu)2cAMP for 1 and 3 days increased ADM mRNA accumulation two- to threefold (P < 0.05). Our results show that ADM mRNA is present not only in adrenal medulla and pheochromocytomas, but also in adrenocortical neoplasms. Both protein kinase A- and C-dependent mechanisms regulate ADM mRNA expression in adrenocortical and pheochromocytoma cells supporting the suggested role for ADM as an autocrine or paracrine (or both) regulator of adrenal function.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Adenoma; Adrenal Cortex; Adrenal Cortex Neoplasms; Adrenal Gland Neoplasms; Adrenal Glands; Adrenomedullin; Blotting, Northern; Carcinoma; Cells, Cultured; Cholesterol Side-Chain Cleavage Enzyme; Enzyme Activation; Enzyme Inhibitors; Gene Expression; Gene Expression Regulation; Humans; Peptides; Pheochromocytoma; Protein Kinase C; RNA, Messenger; Staurosporine; Tetradecanoylphorbol Acetate

Adrenomedullin (AM) is a vasorelaxant peptide that was recently isolated from human pheochromocytoma. In contrast to human (h) AM, which has vasodepressor activity, a synthetic N-terminal fragment of hAM, hAM-(1-25)-NH2 showed vasopressor activity in the anesthetized rat. The N-terminal peptides hAM-1-31)-NH2, hAM-(1-25)-OH, hAM-(1-21)-NH2, acetyl-hAM-(16-21)-NH2, and acetyl-hAM-(16-36)-OH all showed vasopressor activities. The potency of hAM-(1-21)-NH2, acetyl-hAM-(16-21)-NH2 was greater than that of hAM-(1-25)-NH2. Pretreatment with phenoxybenzamine, guanethidine, or reserpine attenuated vasopressor activities of these peptides. These data suggested that vasopressor activity of N-terminal fragment of hAM is due to a stimulation of endogenous catecholamine release.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Anesthesia, General; Animals; Blood Pressure; Consciousness; Guanethidine; Humans; Male; Peptide Fragments; Peptides; Phenoxybenzamine; Pheochromocytoma; Rats; Rats, Sprague-Dawley; Reserpine; Structure-Activity Relationship; Vasodilator Agents

Adrenomedullin (AM), a potent and novel vasodilator 52-residue peptide originally isolated from pheochromocytoma, is processed from a precursor molecule (preproAM) in which another unique 20-residue sequence, termed proadrenomedullin N-terminal 20 peptide (PAMP), exists. Using [125I Tyr0] rat PAMP as a radioligand, we have examined PAMP binding sites in various rat tissues and cultured vascular smooth muscle cells (VSMC) from rat aorta. Specific binding sites for rat PAMP, although very low, were widely distributed in various rat tissues examined. The relatively more abundant sites were present in aorta and adrenal glands, followed by lung, kidney, brain, spleen, and heart. An equilibrium binding study using cultured rat VSMC revealed the presence of a single class of high-affinity [dissociation constant (Kd): 3.5 x 10(-8) M] binding sites for rat PAMP with a maximal binding capacity of 4.5 x 10(6) sites per cell. Binding studies revealed that synthetic rat PAMP(1-19)-NH2 was about 10-fold less potent, and rat PAMP(1-20)-OH and human PAMP were about 20-fold less potent than rat PAMP(1-20)-NH2. SDS-polyacylamide gel electrophoresis after affinity-labeling of membranes from various rat tissues (aorta, adrenal glands, lung) and VSMC revealed a distinct labeled band with the apparent molecular mass of 90 kDa, which was diminished by excess unlabeled rat PAMP. A nonhydrolyzable GTP analog (GTP-gammaS) dose-dependently reduced binding of [125I] rat PAMP to VSMC membranes, while ATP-gammaS had no effect. Neither cyclic AMP nor inositol-1,4,5-triphosphate formation was affected by rat PAMP in rat VSMC. The present study demonstrates for the first time that PAMP receptors are widely distributed in various rat tissues, among which aorta and adrenal glands have the most abundant sites. Our data suggest that PAMP receptors are functionally coupled to G-proteins, although its signal transduction remains obscure. The present study also shows that amidation of C-terminal residue of PAMP is critical for receptor binding. The physiological function of PAMP remains undetermined.

Topics: Adenosine Triphosphate; Adrenal Gland Neoplasms; Adrenal Glands; Adrenomedullin; Animals; Aorta, Thoracic; Binding Sites; Binding, Competitive; Cell Membrane; Cells, Cultured; Cyclic AMP; Endothelins; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Inositol 1,4,5-Trisphosphate; Iodine Radioisotopes; Kinetics; Male; Muscle, Smooth, Vascular; Organ Specificity; Peptide Fragments; Peptides; Pheochromocytoma; Proteins; Radioligand Assay; Rats; Rats, Wistar

Adrenomedullin is a potent vasodilator peptide that was isolated from human pheochromocytoma. But the presence of adrenomedullin in the brain has not been clarified. We studied the presence of adrenomedullin in the human brain obtained at autopsy from 6 subjects by radioimmunoassay, as well as in the human adrenal glands and tumor tissues of pheochromocytoma, ganglioneuroblastoma and neuroblastoma. Immunoreactive adrenomedullin was detected in every region of human brain examined (0.26-1.4 pmol/g wet weight) with the highest concentrations found in thalamus (1.40 +/- 0.39 pmol/g wet weight, mean +/- SEM) and hypothalamus (1.28 +/- 0.48 pmol/g wet weight). Reverse phase high performance liquid chromatography showed that the immunoreactive adrenomedullin in the human brain was eluted in the position of synthetic human adrenomedullin 1-52. High concentrations of immunoreactive adrenomedullin were found in human adrenal glands (12.6 +/- 1.0 pmol/g wet weight, n = 7), pheochromocytoma (4.5 +/- 1.5 pmol/g wet weight, n = 11), ganglioneuroblastoma (2.0 +/- 1.3 pmol/g wet weight, n = 4) and neuroblastoma (0.55 +/- 0.21 pmol/g wet weight, n = 3). The present study has shown that adrenomedullin is present in the human brain in high concentrations, suggesting that adrenomedullin acts as a neurotransmitter, neuromodulator or neurohormone in man.

Topics: Adrenal Gland Neoplasms; Adrenal Glands; Adrenomedullin; Adult; Aged; Brain; Female; Ganglioneuroblastoma; Humans; Male; Middle Aged; Neuroblastoma; Peptides; Pheochromocytoma; Radioimmunoassay; Tissue Distribution

Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide found in adrenomedullin precursor. Using a radioimmunoassay for human PAMP, we purified immunoreactive PAMP (ir-PAMP) from human pheochromocytoma and determined its complete amino acid sequence. The major component of PAMP-like immunoreactivity was found to be PAMP [1-20] NH2 with an amino acid sequence identical to that of the deduced amino acid sequence by cDNA analysis. Both ir-PAMP and ir-adrenomedullin were found to be abundant in normal adrenal medulla as well as pheochromocytoma tissue arising from adrenal medulla, and there was a significantly (p < 0.05) positive correlation between ir-adrenomedullin and ir-PAMP concentrations in these tissues. However, the PAMP/adrenomedullin ratio in pheochromocytoma tissues (0.197 +/- 0.013) was significantly (p < 0.005) lower than that in adrenal medullae (0.384 +/- 0.041). The present data indicate that PAMP is biosynthesized from adrenomedullin precursor, but the biosynthesis or metabolism of PAMP in pheochromocytoma may be different from that of normal adrenal medulla.

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adrenomedullin; Amino Acid Sequence; Antihypertensive Agents; Cadaver; Humans; Molecular Sequence Data; Peptide Biosynthesis; Peptide Fragments; Peptides; Pheochromocytoma; Protein Precursors; Proteins; Radioimmunoassay

Adrenomedullin (AM) is a potent hypotensive peptide recently discovered from human pheochromocytoma tissue by its stimulating activity of platelet cAMP production. In this study, we have isolated the gene for human AM from a human genomic library and determined its structure. The genomic DNA of human AM consists of 4 exons and 3 introns, and the 5' flanking region contains TATA, CAAT and GC boxes. There are also multiple binding sites for activator protein-2 (AP-2) and a cAMP-regulated enhancer element. Southern blot analyses revealed that the AM gene is situated in a single locus of chromosome 11. These indicate that the human AM gene has components for its functional expression and that the expression may be subject to the activity of protein kinase C and the feedback from cAMP level.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Amino Acid Sequence; Animals; Antihypertensive Agents; Base Sequence; Blotting, Southern; Chromosome Mapping; Chromosomes, Human, Pair 11; DNA; Exons; Genomic Library; Hominidae; Humans; Introns; Leukocytes; Molecular Sequence Data; Peptides; Pheochromocytoma; Restriction Mapping

Adrenomedullin is a novel hypotensive peptide recently isolated from human pheochromocytoma. Since a high concentration of immunoreactive adrenomedullin was found in pheochromocytoma tissue, the cDNA library of pheochromocytoma was constructed, and the cDNA clone encoding an adrenomedullin precursor was isolated and sequenced. The precursor for human adrenomedullin (human preproadrenomedullin) is 185 amino acids in length, including an adrenomedullin sequence. Proadrenomedullin (proAM) contains a unique twenty amino acid sequence followed by Gly-Lys-Arg in the N-terminal region. It is possible that a novel 20 residues peptide, termed "proadrenomedullin N-terminal 20 peptide" (proAM-N20) whose carboxy terminus may be Arg-NH2, is processed from proadrenomedullin. By RNA blot analysis, human adrenomedullin mRNA was found to be highly expressed in several tissues including adrenal medulla, ventricle, lung and kidney as well as pheochromocytoma.

Topics: Adrenal Gland Neoplasms; Adrenal Medulla; Adrenomedullin; Amino Acid Sequence; Antihypertensive Agents; Base Sequence; Cloning, Molecular; DNA, Neoplasm; Humans; Molecular Sequence Data; Organ Specificity; Peptide Biosynthesis; Peptides; Pheochromocytoma; Poly A; Protein Precursors; Restriction Mapping; RNA; RNA, Messenger; RNA, Neoplasm; Transcription, Genetic

A novel hypotensive peptide was discovered in human pheochromocytoma by monitoring the elevating activity of platelet cAMP. Since this peptide is abundant in normal adrenal medulla as well as in pheochromocytoma tissue arising from adrenal medulla, it was designated "adrenomedullin". The peptide, consisting of 52 amino acids, has one intramolecular disulfide bond and shows slight homology with calcitonin gene related peptide. It was found to elicit a potent and long lasting hypotensive effect. The peptide circulates in blood in a considerable concentration, but it was not found in brain. These data suggest that adrenomedullin is a new hormone participating in blood pressure control. Occurrence of adrenomedullin indicates the possible existence of a novel system for circulation control.

Topics: Adrenal Gland Neoplasms; Adrenomedullin; Amino Acid Sequence; Animals; Antihypertensive Agents; Blood Platelets; Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Cyclic AMP; Humans; Male; Molecular Sequence Data; Peptides; Pheochromocytoma; Radioimmunoassay; Rats; Rats, Wistar