THE IMPACT OF CHRONIC RENAL FAILURE ON NITRIC OXIDE SYNTHASE ISOFORMS GENE EXPRESSION IN THE PENIS AND PELVIC GANGLIA OF RATS

1. Transport of l-arginine and the nitric oxide synthase inhibitors NG-monomethyl-l-arginine and NG-nitro-l-arginine was investigated in human erythrocytes from healthy donors and uraemic patients on haemodialysis. 2. Although Km values for total l-arginine influx were not significantly different in erythrocytes freshly isolated from controls or uraemic patients, uraemia was associated with an increase in the Vmax for transport (826 compared with 1176 μmol h−1 l−1 of cells) which was reduced to control values after dialysis. 3. Saturable influx of l-arginine was mediated by the classical cationic amino acid transport system y+ and system y+L, known to transport cationic and neutral amino acids with higher affinity. 4. Under zero-trans conditions, the Vmax for l-arginine transport via system y+ increased from 271 to 700 μmol h−1 l−1 of cells in uraemia, while Km values increased from 44 to 94 μmol/l. Dialysis had no significant effect on the kinetic parameters altered by uraemia. 5. Under zero-trans conditions, and with system y+ inhibited by N-ethylmaleimide (0.2 mmol/l), transport of l-arginine via system y+L was unaffected by uraemia. 6. Saturable influx of NG-monomethyl-l-arginine was also mediated by systems y+ (Km = 56 μmol/l, Vmax = 353 μmol h−1 l−1 of cells) and y+L (Km = 17 μmol/l, Vmax = 51.3 μmol h−1 l−1 of cells) and, as with l-arginine, uraemia increased the transport capacity for NG-monomethyl-l-arginine. 7. Influx of the neutral nitric oxide synthase inhibitor NG-nitro-l-arginine was not readily saturable. 8. Intracellular concentrations of l-arginine and NG-monomethyl-l-arginine were significantly increased in erythrocytes from uraemic patients when compared with controls, consistent with an increased transport capacity for l-arginine and NG-monomethyl-l-arginine. 9. The present study provides evidence that system y+ mediates the increased transport of l-arginine and NG-monomethyl-l-arginine in human erythrocytes from patients with chronic renal failure. Our findings may have implications for the activity of the l-arginine—nitric oxide signalling pathway in vascular endothelial and smooth-muscle cells in uraemia.

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Decreased endothelial nitric oxide synthase in gastric mucosa of rats with chronic renal failure

AJP Renal Physiology ◽

10.1152/ajprenal.1998.274.6.f1102 ◽

1998 ◽

Vol 274 (6) ◽

pp. F1102-F1108 ◽

Cited By ~ 1

Author(s):

M. Tomikawa ◽

M. Ohta ◽

N. D. Vaziri ◽

J. D. Kaunitz ◽

R. Itani ◽

...

Keyword(s):

Nitric Oxide ◽

Renal Failure ◽

Blood Flow ◽

Chronic Renal Failure ◽

Nitric Oxide Synthase ◽

Gastric Mucosa ◽

Mucosal Blood Flow ◽

Gastric Mucosal Blood Flow ◽

Enos Mrna ◽

Oxide Synthase

According to recent reports, chronic renal failure (CRF) increases the susceptibility of gastric mucosa to injury. Since nitric oxide plays a major role in gastric mucosal defense and injury, we investigated, in rats with CRF produced by five-sixths nephrectomy and in control rats, the expression of nitric oxide synthase (NOS) in the stomach and measured mucosal and submucosal gastric blood flow. In CRF rats, gastric mucosal blood flow was significantly reduced compared with control rats, whereas submucosal and serosal blood flow was significantly increased. CRF significantly decreased endothelial NOS (eNOS) mRNA abundance by 53% ( P < 0.01) and reduced expression of eNOS protein by 42% ( P < 0.01) compared with the controls. Enzyme activity of eNOS was significantly reduced in gastric mucosa of CRF rats ( P < 0.05). These data are consistent with reduced gastric mucosal blood flow in CRF rats and can explain altered susceptibility of gastric mucosa to injury in CRF rats.

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Downregulation of Neuronal Nitric Oxide Synthase in the Rat Remnant Kidney

Journal of the American Society of Nephrology ◽

10.1681/asn.v104704 ◽

1999 ◽

Vol 10 (4) ◽

pp. 704-713

Author(s):

AGNES ROCZNIAK ◽

JAMES N. FRYER ◽

DAVID Z. LEVINE ◽

KEVIN D. BURNS

Keyword(s):

Nitric Oxide ◽

Renal Failure ◽

Chronic Renal Failure ◽

Nitric Oxide Synthase ◽

Protein Expression ◽

Collecting Duct ◽

Neuronal Nitric Oxide Synthase ◽

No Production ◽

Oxide Synthase ◽

Nnos Expression

Abstract. Chronic renal failure is associated with disturbances in nitric oxide (NO) production. This study was conducted to determine the effect of 5/6 nephrectomy (5/6 Nx) on expression of intrarenal neuronal nitric oxide synthase (nNOS) in the rat. In normal rat kidney, nNOS protein was detected in the macula densa and in the cytoplasm and nuclei of cells of the inner medullary collecting duct by both immunofluorescence and electron microscopy. Western blot analysis revealed that 2 wk after 5/6 Nx, there were significant decreases in nNOS protein expression in renal cortex (sham: 95.42 ± 15.60 versus 5/6 Nx: 47.55 ± 12.78 arbitrary units, P < 0.05, n = 4) and inner medulla (sham: 147.70 ± 26.96 versus 5/6 Nx: 36.95 ± 17.24 arbitrary units, P < 0.005, n = 8). Losartan treatment was used to determine the role of angiotensin II (AngII) AT1 receptors in the inhibition of nNOS expression in 5/6 Nx. Losartan had no effect on the decreased expression of nNOS in the inner medulla, but partially increased nNOS protein expression in the cortex of 5/6 Nx rats. In contrast, in sham rats losartan significantly inhibited nNOS protein expression in the cortex (0.66 ± 0.04-fold of sham values, P < 0.05, n = 6) and inner medulla (0.74 ± 0.12-fold of sham values, P < 0.05, n = 6). nNOS mRNA was significantly decreased in cortex and inner medulla from 5/6 Nx rats, and the effects of losartan on nNOS mRNA paralleled those observed on nNOS protein expression. These data indicate that 5/6 Nx downregulates intrarenal nNOS mRNA and protein expression. In normal rats, AngII AT1 receptors exert a tonic stimulatory effect on expression of intrarenal nNOS. These findings suggest that the reduction in intrarenal nNOS expression in 5/6 Nx may play a role in contributing to hypertension and altered tubular transport responses in chronic renal failure.

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