cyclic-gmp and Uremia

Red blood cells (RBCs) have been found to synthesize and release both nitric oxide (NO) and cyclic guanosine monophosphate (cGMP), contributing to systemic NO bioavailability. These RBC functions resulted impaired in chronic kidney disease (CKD). This study aimed to evaluate whether predialysis (conservative therapy, CT) and dialysis (peritoneal dialysis, PD; hemodialysis, HD) therapies used during CKD progression may differently affect NO-synthetic pathway in RBCs. Our data demonstrated that compared to PD, although endothelial-NO-synthase activation was similarly increased, HD and CT were associated to cGMP RBCs accumulation, caused by reduced activity of cGMP membrane transporter (MRP4). In parallel, plasma cGMP levels were increased by both CT and HD and they significantly decreased after hemodialysis, suggesting that this might be caused by reduced cGMP renal clearance. As conceivable, compared to healthy subjects, plasma nitrite levels were significantly reduced by HD and CT but not in patients on PD. Additionally, the increased carotid intima-media thickness (IMT) values did not reach the significance exclusively in patients on PD. Therefore, our results show that PD might better preserve the synthetic NO-pathway in CKD-erythrocytes. Whether this translates into a reduced development of uremic vascular complications requires further investigation.

Topics: Aged; Cyclic GMP; Erythrocytes; Female; Humans; Kidney Failure, Chronic; Male; Middle Aged; Models, Biological; Multidrug Resistance-Associated Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitrites; Nitrosation; Peritoneal Dialysis; Phosphorylation; Renal Dialysis; Uremia

Pregnancy worsens renal function in females with chronic renal failure (CRF) through an unknown mechanism. Reduced nitric oxide (NO) generation induces renal injury. Arginine transport by cationic amino acid transporter-1 (CAT-1), which governs endothelial NO generation, is reduced in both renal failure and pregnancy. We hypothesize that attenuated maternal glomerular arginine transport promotes renal damage in CRF pregnant rats. In uremic rats, pregnancy induced a significant decrease in glomerular arginine transport and cGMP generation (a measure of NO production) compared with CRF or pregnancy alone and these effects were prevented by l-arginine. While CAT-1 abundance was unchanged in all experimental groups, protein kinase C (PKC)-α, phosphorylated PKC-α (CAT-1 inhibitor), and phosphorylated CAT-1 were significantly augmented in CRF, pregnant, and pregnant CRF animals; phenomena that were prevented by coadministrating l-arginine. α-Tocopherol (PKC inhibitor) significantly increased arginine transport in both pregnant and CRF pregnant rats, effects that were attenuated by ex vivo incubation of glomeruli with PMA (a PKC stimulant). Renal histology revealed no differences between all experimental groups. Inulin and p-aminohippurate clearances failed to augment and renal cortical expression of hypoxia inducible factor-1α (HIF-1α) significantly increased in CRF pregnant rat, findings that were prevented by arginine. These studies suggest that in CRF rats, pregnancy induces a profound decrease in glomerular arginine transport, through posttranslational regulation of CAT-1 by PKC-α, resulting in attenuated NO generation. These events provoke renal damage manifested by upregulation of renal HIF-1α and loss of the ability to increase glomerular filtration rate during gestation.

Topics: Animals; Arginine; Biological Transport, Active; Blotting, Western; Cationic Amino Acid Transporter 1; Chromatography, High Pressure Liquid; Cyclic GMP; Female; Glomerular Filtration Rate; Hypoxia-Inducible Factor 1, alpha Subunit; Immunoprecipitation; Inulin; Kidney Glomerulus; Nitric Oxide Synthase Type III; p-Aminohippuric Acid; Phosphorylation; Pregnancy; Pregnancy Complications; Protein Kinase C-alpha; Rats; Rats, Wistar; Renal Circulation; Uremia; Vitamin E

Malnutrition is a common feature in chronic renal failure and adversely affects patient morbidity and mortality. We here investigate the effects of nutritional status on the L-arginine-nitric oxide signaling pathway and platelet function in chronic renal failure patients on regular hemodialysis.. Platelet aggregation was correlated with plasma amino acid profiles, L-arginine transport, and nitric oxide synthase (NOS) activity determined by conversion of L-[(3)H]-arginine to L-[(3)H]-citrulline and accumulation of intracellular cyclic guanosine monophospate (cGMP) in platelets from malnourished and well-nourished chronic renal failure patients on regular hemodialysis (N = 78).. Transport of L-arginine (pmol/10(9)cells/min) via y(+) L system was increased in well-nourished (104 +/- 15) compared to controls (57 +/- 11) or malnourished chronic renal failure patients (55 +/- 13). Basal NOS activity (pmol/10(8)cells) was enhanced in well-nourished chronic renal failure patients (0.51 +/- 0.01) compared to controls (0.18 +/- 0.01) or malnourished chronic renal failure patients (0.08 +/- 0.03). In addition, basal cGMP levels are elevated in platelets from well-nourished chronic renal failure compared to malnourished uremic patients. Platelet aggregation induced by collagen is impaired in well-nourished chronic renal failure patients compared to malnourished patients and controls. Plasma L-arginine levels are reduced in chronic renal failure patients and even lower in malnourished patients.. Our findings provide the first evidence that L-arginine transport via the high affinity system y(+) L and nitric oxide synthesis are only stimulated in platelets from well-nourished chronic renal failure patients, leading to impaired platelet aggregation. The absence of this adaptive response in the l-arginine-nitric oxide pathway in platelets from malnourished chronic renal failure patients may account for the enhanced occurrence of thrombotic events in these patients.

Topics: Adult; Aged; Amino Acids; Arginine; Blood Platelets; Cyclic GMP; Female; Humans; Kidney Failure, Chronic; Male; Malnutrition; Middle Aged; Nitric Oxide; Nitric Oxide Synthase; Nutritional Status; Platelet Aggregation; Renal Dialysis; Tumor Necrosis Factor-alpha; Uremia

NG-monomethyl-L-arginine (L-NMMA) decreases the expression of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) and increases the expression of GATA-2 mRNA and levels of GATA-2 binding activity, thereby inhibiting erythropoietin (Epo) promoter activity and causing a decrease in the expression of Epo protein. In the present study, we examined the effect of L-arginine on Epo gene expression in Hep3B cells and BDF1 mice.. Hep3B cells were incubated with and without different concentrations of L-NMMA and/or l-arginine. Anemic mice were injected with phosphate-buffered saline (PBS) or L-NAME and L-arginine.. Incubation with L-NMMA under hypoxic conditions inhibited Epo expression, but this inhibition was recovered by the addition of L-arginine. Hypoxia induced the secretions of NO and cGMP, but the addition of L-NMMA inhibited these inductions, though these inhibitions of NO and cGMP by L-NMMA were recovered by the addition of L-arginine. Hep3B cells transfected with the Epo promoter/enhancer-luciferase gene had Epo promoter activity. This activity was inhibited by L-NMMA, but it could be recovered by the addition of L-arginine. L-NMMA induced the binding activity of GATA-2 under hypoxic conditions. This binding activity was inhibited by the addition of L-arginine. The addition of cGMP inhibited L-NMMA-induced GATA-2 binding activity in a dose-dependent manner. The results of an in vivo mouse assay revealed that L-NAME inhibited the expression of Epo, but this inhibition of Epo expression by L-NAME was rescued by pretreatment with L-arginine.. L-arginine rescues decreased erythropoietin gene expression by stimulating GATA-2 with NG-monomethyl-L-arginine.

Topics: Anemia; Animals; Arginine; Cell Hypoxia; Cells, Cultured; Cyclic GMP; DNA-Binding Proteins; Enzyme Inhibitors; Erythropoietin; GATA2 Transcription Factor; Gene Expression; Humans; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; omega-N-Methylarginine; Oxygen; Promoter Regions, Genetic; RNA, Messenger; Transcription Factors; Uremia

Nitric oxide (NO) is produced in excess in various pathological states, including sepsis and hepatic cirrhosis, and appears to be related to inflammatory status. In uremia, one would expect the levels of NO to increase. We aimed to determine whether hemodialysis (HD) would remove NO from the systemic circulation of uremic patients. Blood was collected before, after, and 1 day after HD from 12 uremic patients. Plasma nitrite and nitrate (NOx-) levels were measured by colorimetric Greiss reaction and cGMP was measured by an enzyme immunoassay kit. Our study demonstrated that uremic patients have high plasma NO levels, and HD led to a significant drop in plasma NOx- level (63 +/- 15% reduction). The level rose back to the pre-HD level on the following day. Plasma cGMP in the patients also decreased significantly after HD (27 +/- 14% reduction). In conclusion, we hypothesized that HD might be a possible approach for the removal of excess NO in pathological conditions such as sepsis and hepatic cirrhosis.

Topics: Colorimetry; Cyclic GMP; Female; Follow-Up Studies; Humans; Inflammation Mediators; Kidney Failure, Chronic; Liver Cirrhosis; Male; Middle Aged; Nitrates; Nitric Oxide; Nitrites; Renal Dialysis; Sepsis; Uremia

1. There is no experimental proof that renal insufficiency is a necessary condition for hypertension during erythropoietin treatment. 2. The present study compares the effect of 3 weeks treatment with r-hu EPO (50 i.u./kg) on systolic blood pressure (SBP), haematocrit and plasma cGMP in an animal model of chronic renal failure (remnant kidney model excision) and sham-operated rats. 3. Sub-total nephrectomy induced a significant fall in haematocrit and a significant increase in plasma creatinine levels. Treatment with r-hu EPO resulted in a significant haematocrit increase in uraemic as well as in non-uraemic rats. Despite this effect, r-hu EPO treatment had no effect on SBP in sham-operated rats. On the contrary, this treatment caused significant SBP elevation in uraemic rats; in these rats, SBP increase did not correlate with haematocrit increase. 4. Plasma cGMP concentrations were significantly higher in uraemic compared to sham-operated rats and were not modified by r-hu EPO treatment. 5. This study provides evidence that renal insufficiency in rats is a prerequisite for the development of hypertension during erythropoietin treatment.

Topics: Animals; Blood Pressure; Creatinine; Cyclic GMP; Disease Models, Animal; Erythropoietin; Hematocrit; Hypertension; Kidney Failure, Chronic; Male; Nephrectomy; Rats; Rats, Wistar; Uremia

It is our intention to isolate, purify, and characterize the putative low-molecular-weight "natriuretic hormone" responsible for extracellular fluid (ECF) homeostasis. Toward this end, we are purifying from human uremic urine, and identifying endogenous vasopressor and natriuretic compounds. Bioactive components from large volumes of pooled urine were purified by ultrafiltration (< or = 3 kDa), gel filtration chromatography, and sequential reverse-phase and normal-phase high-performance liquid chromatography (HPLC). After each HPLC step, the fractions were evaluated in vivo, were assayed for inhibition of Na+/K(+)-ATPase-mediated 86Rb+ uptake, and were checked for cross-reactivity with an anti-ouabain antibody. Fractions assayed in vivo were identified that induced natriuresis, altered mean arterial pressure, or increased plasma cyclic-GMP. Also, many fractions inhibited Na+/K(+)-ATPase and/or cross-reacted with anti-ouabain antibody. None of the in vitro assays correlates with natriuretic or pressor effects. This plethora of bioactivities, revealed only with increased sample purity, may account for much of the confusion and multiplicity of crude isolates claimed to be the putative hormone. Presently we are attempting to purify and identify these natriuretic materials. One of these, a 3-substituted indole, has been partially characterized.

Topics: Animals; Biological Assay; Blood Pressure; Chromatography, Gel; Chromatography, High Pressure Liquid; Cross Reactions; Cyclic GMP; Humans; Magnetic Resonance Spectroscopy; Natriuresis; Natriuretic Agents; Ouabain; Radioimmunoassay; Rubidium; Sodium-Potassium-Exchanging ATPase; Uremia

In order to evaluate the hormonal regulation of blood pressure (BP) in uraemia 12 patients on chronic maintenance dialysis and 14 healthy controls were studied. BP and plasma concentrations of atrial natriuretic peptide (ANP), cyclic 3',5'-guanosine monophosphate (cGMP), and intact parathyroid hormone (PTH(1-84)) were determined before, during, and after a 60 min noradrenaline infusion 0.1 micrograms kg-1 body wt. min-1. Mean BP increased to the same extent in the uraemic patients (median 15 mmHg, range 6-25 mmHg) as in the controls (12 mmHg, 5-25 mmHg). ANP increased during noradrenaline infusion both in patients (7.2 to 8.3 pmol/l, medians, p < 0.01) and in controls (4.4 to 6.0 pmol/l, p < 0.01), and so did cGMP (patients: 31.6 to 35.9 nmol/l, p < 0.05; controls: 6.6 to 8.7 nmol/l, p < 0.01). PTH(1-84) was higher in the uraemic patients than in the controls, but was unchanged during noradrenaline infusion in both groups. Correlation analyses gave no evidence of a direct relation between BP and ANP, but basal PTH(1-84) was negatively correlated to basal mean BP in the patients (rho = -0.615, p < 0.05), but not in the controls. In conclusion, noradrenaline induced similar elevations of BP in dialysis patients as in healthy controls despite elevated ANP and PTH(1-84) in the patients, and ANP release was stimulated in both groups. PTH(1-84) may participate in blood pressure regulation in uraemic patients.

Topics: Adult; Atrial Natriuretic Factor; Blood Pressure; Cyclic GMP; Female; Heart Rate; Humans; Infusions, Intravenous; Male; Middle Aged; Norepinephrine; Parathyroid Hormone; Renal Dialysis; Uremia

1. Eleven patients on chronic maintenance dialysis were investigated before and after intravenous bolus injection of atrial natriuretic peptide (2 micrograms/kg body weight). 2. Mean blood pressure was reduced to the same extent in the uraemic patients as in 11 healthy subjects, with a nadir 3 min after the atrial natriuretic peptide injection at which time mean blood pressure was reduced by 13% (median) in the uraemic patients and 11% in the healthy subjects. 3. Basal plasma atrial natriuretic peptide and guanosine 3':5'-cyclic monophosphate levels were higher in the uraemic patients than in the healthy subjects, but guanosine 3':5'-cyclic monophosphate increased markedly in both groups after atrial natriuretic peptide injection. 4. Using changes in gamma-emission from blood after previous labelling of erythrocytes with 51Cr, and changes in packed cell volume, haemoglobin and erythrocyte count, a reversible shift of fluid from the intravascular phase was demonstrated in the uraemic subjects. The blood volume was maximally reduced by 6% (median) of initial blood volume at 30 min after atrial natriuretic peptide injection. 5. Correlation analyses gave no evidence of a causal relationship between the changes in mean blood pressure and changes in blood volume, angiotensin II, aldosterone or arginine vasopressin after atrial natriuretic peptide injection. 6. It is concluded that a pharmacological dose of atrial natriuretic peptide reduces blood pressure in uraemic patients on maintenance dialysis to the same extent as in healthy subjects. The blood-pressure-reducing effect of atrial natriuretic peptide does not seem to be mediated by its diuretic effect or ability to displace fluid from plasma to the interstitial fluid compartment.

Topics: Adult; Aldosterone; Angiotensin II; Arginine Vasopressin; Atrial Natriuretic Factor; Blood Pressure; Blood Volume; Cyclic GMP; Female; Heart Rate; Humans; Male; Middle Aged; Uremia

Topics: Adult; Aged; Cyclic AMP; Cyclic GMP; Humans; Levamisole; Middle Aged; Rosette Formation; T-Lymphocytes; Uremia