cyclic-gmp and Anemia

Topics: Anemia; Animals; Biological Assay; Chemical Phenomena; Chemistry; Culture Techniques; Cyclic AMP; Cyclic GMP; DNA; Erythroblasts; Erythropoiesis; Erythropoietin; Humans; Kidney; Liver; Mice; Polycythemia; Polycythemia Vera; Prostaglandins E; Radioimmunoassay; Rats; RNA; RNA, Messenger; Sheep

Endothelial nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) contribute to erythropoietin (EPO)-induced hypertension, a major adverse reaction associated with EPO therapy. To investigate the mechanism of EPO-induced hypertension, we examined circulating endothelial progenitor cells (EPCs) taken from 56 hemodialysis (HD) patients. Among these EPCs (which reflect the condition of the endothelium), we looked for EPO receptor (EPOR) mRNAs. A truncated form of EPOR acts as a dominant negative regulator of EPO signaling, leading to hypertension. We found that the ratio of truncated EPOR mRNA in EPCs has a correlation with EPO-induced increase in blood pressure (r = 0.36, P = 0.02). The ratio of truncated to total EPOR mRNA in EPCs had an inverse correlation with EPO-induced cGMP production in vitro (r = -0.31, P = 0.02). A similar correlation was observed in cultured human endothelial cells after transfection of the full-length or truncated forms of EPOR (r = -0.92, P < 0.001). It follows, therefore, that evaluation of EPOR isoform mRNA in EPCs can predict EPO-induced hypertension. The termination of the EPO signal by truncated EPORs may decrease NO/cGMP production after EPO exposure, thereby raising blood pressure.

Topics: Adult; Aged; Aged, 80 and over; Anemia; Cells, Cultured; Cyclic GMP; DNA, Complementary; Endothelial Cells; Erythropoietin; Female; Humans; Hypertension; Male; Middle Aged; Multivariate Analysis; Nitric Oxide; Polymerase Chain Reaction; Receptors, Erythropoietin; Recombinant Proteins; Renal Dialysis; RNA, Messenger; Signal Transduction; Stem Cells; Transfection; Up-Regulation

Erythropoietin (EPO) and its analogs increase blood pressure (BP) in susceptible patients. The ratio of truncated to full EPO receptors (EPORs) in endothelial progenitor cells harvested from anemic patients receiving EPO while undergoing hemodialysis is related to the increased BP observed in these patients. Truncated EPORs exert a hypertensive effect by opposing full EPOR stimulation that augments cyclic guanosine monophosphate (GMP) in vascular endothelium. The contribution of this discovery to clinical practice is debatable.

Topics: Anemia; Cyclic GMP; Disease Susceptibility; Endothelial Cells; Hematinics; Humans; Hypertension; Multivariate Analysis; Receptors, Erythropoietin; Renal Dialysis; RNA, Messenger; Stem Cells

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

Chronic fetal anemia causes polyhydramnios and fetal hydrops and is associated with increased fetal diuresis and natriuresis. To determine the role of atrial natriuretic peptide (ANP) in the renal adaptation to chronic fetal anemia we studied the effects of HS-142-1 (HS), a specific inhibitor of the guanylate cyclase-linked ANP receptor (ANP-GC), in two groups of chronically instrumented unanesthetized sheep fetuses. Seven fetuses were made anemic by serial isovolemic hemorrhage over 1 wk, and five fetuses served as nonanemic controls. Over the 7 d of hemorrhage ANP concentrations increased (45 +/- 7 to 234 +/- 15 fmol/mL). Hematocrit and arterial blood oxygen content were significantly lower in the anemic compared with the nonanemic fetuses (13.8 +/- 0.7 versus 34.6 +/- 2.3% and 0.7 +/- 0.1 versus 2.6 +/- 0.2 mmol/L). Before HS urine flow rate, urinary sodium excretion, fractional excretion of sodium, and renal blood flow were increased in the anemic fetuses, and the extracellular fluid volume (inulin space) was increased (674 +/- 94 versus 497 +/- 71 mL/kg). However, GFR was not different between the groups. HS caused a significant increase in the central venous pressure of the anemic fetuses (0.49 +/- 0.03 to 0.70 +/- 0.05 kPa). Urinary excretion of cGMP was considered to be a marker of endogenous ANP renal effect and was measured before and after a single bolus of HS (5.2 +/- 0.30 mg/kg). HS decreased urinary cGMP excretion to 50 and 37% of baseline levels in anemic and nonanemic fetuses, respectively. Urine flow decreased in both nonanemic and anemic fetuses (0.48 +/- 0.13 to 0.25 +/- 0.06 and 1.30 +/- 0.66 +/- 0.06 mL/min). Sodium excretion decreased in both groups after HS (19 +/- 5 to 9 +/- 2 and 83 +/- 16 to 39 +/- 5 mumol/min). GFR decreased after HS (3.0 +/- 0.8 to 2.4 +/- 0.5 and 3.6 +/- 0.3 to 2.6 +/- 0.2 mL/min. Fraction excretion of sodium also decreased in both groups after HS (4.6 +/- 2.7 to 2.7 +/- 0.5 and 16.1 +/- 2.4 to 11 +/- 1.6). Percent decreases in urine flow, sodium excretion, GFR, and fractional excretion of sodium observed in the anemic fetuses were not statistically different from the nonanemic fetuses. Urine flow and sodium excretion did not decrease to control levels after HS, suggesting that factors in addition to ANP contribute to the natriuresis seen with chronic anemia. After HS a transient increase in renal blood flow was observed in the nonanemic fetuses. An immediate and sustained further increase in renal blood flow

Topics: Anemia; Animals; Atrial Natriuretic Factor; Carbon Dioxide; Cattle; Chronic Disease; Cyclic GMP; Disease Models, Animal; Fetal Diseases; Hemodynamics; Oxygen; Polysaccharides; Receptors, Atrial Natriuretic Factor; Sheep; Sodium

The studies were carried out on male Wistar rats. The animals were divided into two groups: control and experimental. The hematocrit value and reticulocyte count were determined in blood samples collected from control and experimental rats. The experimental rats received subcutaneous injections of phenylhydrazine manufactured by Sigma for the duration of 3 days. On the 5th day blood samples were collected from all the control and experimental animals and determinations of hematocrit and reticulocyte count were repeated. cAMP levels were determined in bone marrow extracts by means of a radiocompetitive method. The cGMP level was determined by a radioimmunological assay. A significant elevation of cAMP level was detected in experimental rats, whereas the cGMP level changed only slightly.

Topics: Anemia; Animals; Bone Marrow; Cyclic AMP; Cyclic GMP; Hematocrit; Male; Phenylhydrazines; Rats; Rats, Inbred Strains; Reticulocytes