beta-endorphin and Pheochromocytoma

Pro-opiomelanocortin gene expression is a ubiquitous phenomenon which takes place not only in the pituitary but also in many normal and tumoral non-pituitary tissues. However, the clinical features of the ectopic ACTH syndrome are rarely encountered. To further investigate this problem we examined series of normal human pituitaries and endocrine tumours evaluating the tissue content of pro-opiomelanocortin peptides, and the state of neuroendocrine differentiation as indicated by the biochemical marker 7B2.. Tissue concentration of 7B2, pro-opiomelanocortin products (joining peptide and beta-endorphin) were measured in 13 pituitary corticotrophic adenomas and 13 non-pituitary tumours associated with the ectopic ACTH syndrome (five out of 20 bronchial carcinoid tumours, two out of 19 phaeochromocytomas, one out of 11 medullary thyroid carcinomas, three pancreatic and two thymic carcinoid tumours). Molecular weight forms of immunoreactive 7B2 and 7B2 RNA messenger were determined using Western and Northern blot analysis respectively.. In all tissues examined, concentrations of immunoreactive beta-endorphin (fmol/mg tissue wet weight) showed widely distributed values from less than 0.7 to 1,340,000, which were correlated (r = 0.975, P less than 0.01) with that of immunoreactive joining peptide, another pro-opiomelanocortin fragment. In the 13 non-pituitary tumours associated with the ectopic ACTH syndrome, immunoreactive beta-endorphin concentrations ranged from 8.6 to 548,000, whereas in normal and tumoral pituitaries they varied from 16,600 to 364,800, and 5000 to 1,340,000, respectively. Immunoreactive 7B2 was detected in 67 of 68 neuroendocrine tumours. Tissue concentrations (fmol/mg tissue wet weight) of immunoreactive 7B2 varied from 135 to 1787 in pituitary tumours; from less than 0.5 to 555 in bronchial carcinoids; from 21.7 to 793 in phaeochromocytomas; from less than 1.6 to 948 in medullary thyroid carcinomas. Western blot analysis showed a predominant molecular weight form of immunoreactive 7B2 at 22 kDa. Northern blot analysis of RNA extracted from ACTH secreting pituitary and non-pituitary tumours showed a predominant signal hybridizing at 1.5 kb with a 7B2 probe.. These results show that all ACTH secreting tumours have biochemical markers for neuroendocrine differentiation. Tissue concentrations of pro-opiomelanocortin peptides are variable, being extremely high in the most benign tumours and low in those with an aggressive growing pattern, and are not correlated with the biochemical neuroendocrine markers.

Topics: ACTH Syndrome, Ectopic; Adenoma; beta-Endorphin; Biomarkers, Tumor; Bronchial Neoplasms; Carcinoid Tumor; Humans; Nerve Tissue Proteins; Neuroendocrine Secretory Protein 7B2; Pancreatic Neoplasms; Pheochromocytoma; Pituitary Gland; Pituitary Hormones; Pituitary Neoplasms; Pro-Opiomelanocortin; RNA, Messenger; Thyroid Neoplasms

The immunoreactive (IR) human N-terminal (hNT) of pro-opiomelanocortin (POMC) was measured by specific radioimmunoassay (RIA) and characterized by molecular sieving chromatography, concanavalin A-affinity chromatography and reversed-phase high-performance liquid chromatography (HPLC). The IR hNT levels were 380 +/- 144 ng/g wet wt (mean +/- SD) in the adrenal medulla (N:6), 21.6 +/- 6 ng/g wet wt in the adrenal cortex (N:6), and 45.6% ng/g wet wt in pheochromocytoma tissues (N:3). The IR hNT content of the adrenal medulla was found to be at least twice as high as that of the IR ACTH on a molar basis. Molecular sieving chromatography of IR hNT and IR gamma-3-melanotropin (MSH) showed two major molecular forms (apparent molecular weights of 14 and 12 kilodalton). These major forms were also separable using reversed-phase HPLC. In addition, a part of the IR ACTH material from the adrenal medulla extracts was eluted with an apparent molecular weight of 12 kilodalton. This latter form of IR ACTH was also separated from authentic human ACTH (1-39) by HPLC. Results obtained from concanavalin A-agarose chromatography suggest that one part of the IR gamma-3-MSH material from the adrenal medulla might be non-glycosylated. These results indicate the presence of IR hNT and IR gamma-3-MSH-like material in the human adrenal and also suggest a different processing pathway for POMC from that in the pituitary gland.

Topics: Adrenal Cortex; Adrenal Gland Neoplasms; Adrenal Medulla; Adrenocorticotropic Hormone; beta-Endorphin; Chromatography, Affinity; Chromatography, Gel; Chromatography, High Pressure Liquid; Epinephrine; Humans; Molecular Weight; Neurotensin; Pheochromocytoma; Pro-Opiomelanocortin; Radioimmunoassay

Topics: Adolescent; Adrenal Gland Neoplasms; Adult; Aged; beta-Endorphin; Female; Humans; Male; Middle Aged; Pheochromocytoma

To investigate the possible release of beta-endorphins (beta EN) from tumors and to investigate their possible involvement in the hypotensive mechanism of clonidine (CLO) in pheochromocytoma (PHEO), as compared with essential hypertension (EH), we studied 12 patients with PHEO, 17 patients with uncomplicated stable EH (SEH), nine patients with borderline EH (BEH), and seven healthy volunteers (N). All subjects were hospitalized and excreted normal amounts of sodium. Mean blood pressure (MAP) and plasma beta EN, norepinephrine (NE), epinephrine (E), and dopamine (DA) were measured before and 180 min after an oral dose of 0.3 mg CLO. Following CLO, a significant (p less than 0.01) decrease in MAP was present in all groups. Plasma NE and E decreased (p less than 0.02 to p less than 0.01) in N, BEH, and SEH, but not in PHEO. DA did not change in any group. Pretreatment beta EN did not differ significantly between the groups, and following CLO it did not change in N or PHEO, while it increased significantly in BEH (p less than 0.01) and in SEH (p less than 0.02). Absolute changes in MAP correlated with those of beta EN only in the SEH group. Changes in NE or E did not correlate with changes in MAP in either group. Likewise, changes in NE or E were not correlated with those of beta EN, in N or EH, but a correlation between resting plasma E and resting beta EN concentrations was demonstrated in PHEO. These results support a role of beta EN in the hypotensive action of CLO in EH, but not in N or PHEO.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adrenal Gland Neoplasms; Adult; beta-Endorphin; Blood Pressure; Catecholamines; Clonidine; Dopamine; Female; Humans; Hypertension; Male; Middle Aged; Neurotransmitter Agents; Pheochromocytoma; Time Factors

The expression of opioid receptors and GTP-binding proteins was studied in 14 pheochromocytomas. The amounts of [3H]diprenorphine bound to membranes varied from 13 to 62 fmole/mg protein, but significantly higher in adrenaline-secreting tumors than in noradrenaline-secreting tumors. None of [3H]DADLE, [125I]beta-endorphin or [3H]ethylketocyclazocine binding was correlated with [3H]diprenorphine binding. Gpp(NH)p inhibition of [3H]DADLE binding was evident in all four normal human adrenal medullae but in only 8 out of 14 pheochromocytomas. The extent of Gpp(NH)p inhibition was not correlated with the amount of pertussis toxin (PT)-sensitive GTP-binding proteins as measured by PT-catalyzed [32P]ADP-ribosylation. The present findings suggest that opioid receptors and PT-sensitive GTP-binding proteins are variously expressed in transformed chromaffin cells, pheochromocytoma.

Topics: Adrenal Gland Neoplasms; beta-Endorphin; Cell Membrane; Cyclazocine; Diprenorphine; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Ethylketocyclazocine; GTP-Binding Proteins; Humans; Pheochromocytoma; Receptors, Opioid

Immunohistochemical investigations were carried out on 16 pheochromocytomas for a study of their immunoreactivity to methionine-enkephalin, vasoactive intestinal peptide, somatostatin, corticotropin, beta-endorphin, and calcitonin on serial semithin araldite sections. All antiserums except anti-beta-endorphin, selectively stained a variable number of distinct tumor cells. Methionine-enkephalin-immunoreactive cells were the most frequent. The neuropeptide content of pheochromocytomas appears highly diverse and unpredictable. These findings are supportive of the concept of multisecretory APUD cells of neural crest origin and rule out any of these neuropeptides as reliable immunohistochemical markers for tumor chromaffin cells.

Topics: Adolescent; Adrenal Gland Neoplasms; Adrenocorticotropic Hormone; Adult; beta-Endorphin; Calcitonin; Endorphins; Enkephalin, Methionine; Female; Histocytochemistry; Humans; Immunoenzyme Techniques; Male; Middle Aged; Pheochromocytoma; Somatostatin; Vasoactive Intestinal Peptide

A 47-year old woman is presented who had a left adrenal pheochromocytoma with manifestations also indicative of ectopic ACTH syndrome. The excised adrenal gland showed both an adrenal medullary tumor and adrenal cortical hyperplasia. Immunostaining also showed the presence in the tumor of ACTH and beta endorphins. The immediate post-adrenalectomy decline of catecholamines, ACTH, cortisol and beta endorphins indicate that the adrenal itself was the source of these hormones. This patient, the thirteenth now reported in the literature, represents one form of ectopic ACTH syndrome in which the lesion is benign, and in which a successful outcome can be anticipated.

Topics: Adrenal Cortex; Adrenal Cortex Function Tests; Adrenal Gland Neoplasms; Adrenal Medulla; Adrenocorticotropic Hormone; beta-Endorphin; Catecholamines; Dexamethasone; Endorphins; Female; Histocytochemistry; Humans; Immunoenzyme Techniques; Middle Aged; Pheochromocytoma

Specific enkephalin binding was found in a rat pheochromocytoma cell line, PC12 (subclone h), when cultured in the presence of nerve growth factor (NGF; 50 ng/ml). Specific binding of [3H][D-Ala2]Met-enkephalinamide was saturable with a KD=2.4 nM and Bmax = 866 fmol/mg of protein. The binding was displaced completely by morphine and naloxone at a concentration of 10(-4) and 10(-6) M, respectively. beta-Endorphin and dynorphin [1-13] also displaced the binding; KI = 9.6 and 81.6 nM, respectively. Enkephalin binding in PC12h cells cultured in the absence of NGF was very low. Binding was dramatically increased when cultured in the presence of NGF for 7 to 10 days. The enkephalin binding was induced by NGF in the cells cultured in a hormone-supplemented serum-free medium. In contrast, epidermal growth factor was of two orders lower potency, and insulin had no effect on the expression of enkephalin binding sites. Since the differentiation effects of NGF on PC12h cells are though to offer a model system to investigate the effect of NGH on neurons, the present observations may suggest a physiological role for NGF in the induction and maintenance of specific opiate receptors during development of the autonomic nervous system.

Topics: Animals; beta-Endorphin; Cell Line; Endorphins; Enkephalin, Methionine; Enkephalins; Kinetics; Morphine; Naloxone; Nerve Growth Factors; Pheochromocytoma; Rats; Receptors, Opioid

Tissue concentrations of immunoreactive lipotrophin, beta-endorphin, and met-enkephalin were determined in 10 phaeochromocytomas, 3 of which were responsible for the ectopic ACTH syndrome. Lipotrophin and beta-endorphin immunoreactivities could be detected in all cases, whether or not Cushing's syndrome was present, and their tissue concentrations were significantly correlated (r = 0.95, P less than 0.001). Chromatographic studies showed that gamma-lipotrophin and beta-endorphin were the main peptides in the tumours. Met-enkephalin immunoreactivity was also found in all tumours examined, at much higher concentration and showing no correlation with either lipotrophin or beta-endorphin immunoreactivity. Although beta-endorphin and met-enkephalin are thought to originate from different precursor molecules, these data show that the two opioid peptides may be secreted by the same tumour. The evidence for excess secretion of opioid peptides and their pathological significance in phaeochromocytomas remain to be established.

Topics: Adolescent; Adrenal Gland Neoplasms; Adrenocorticotropic Hormone; Adult; Aged; beta-Endorphin; beta-Lipotropin; Chromatography, Gel; Endorphins; Enkephalin, Methionine; Female; Humans; Male; Middle Aged; Pheochromocytoma