Intrarenal distribution of renal blood flow after acute and chronic administration of nitric oxide-synthase inhibitor.
The effects of acute and chronic inhibition of endothelium derived relaxing factor (EDRF/NO) synthesis were investigated on the intrarenal blood flow in anaesthetized rats. N omega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg) was used for inhibition of NO-synthase. In acute experiments L-NAME was infused, while in chronic experiments L-NAME (4-day pretreatment) was dissolved in the drinking water. Blood flow was measured by 86-Rubidium accumulation method. Renal blood flow decreased markedly after both acute and chronic L-NAME treatment. (Acute: RBF-control: 679 +/- 122, RBF-L-NAME: 333 +/- 65 ml/min/100 g, p < 0.01; Chronic: RBF-control: 527 +/- 133, RBF-L-NAME: 315 +/- 75 ml/min/100 g, p < 0.01). The consequences of the NO-synthase blockade are different in the cortical and medullary vessels. The increase in the vascular resistance in the medulla (in acute experiments 228%, R-control: 2.76 +/- 0.76, R-L-NAME: 9.08 +/- 4.36 R, p < 0.01; in chronic experiments 113%, R-control: 3.89 +/- 1.20, R-NAME: 8.31 +/- 3.75 R, p < 0.01) is appreciably greater than in the cortex (acute blockade: 112%, R-control: 1.12 +/- 0.29, R-L-NAME: 2.38 +/- 0.47 R, p < 0.01; chronic blockade: 62%, R-control: 1.61 +/- 1.03, R-L-NAME: 2.61 +/- 0.61 R, p < 0.01). The percentile distribution of intrarenal blood flow shifts from the medulla toward the cortex following acute NO-synthase blockade (MBF-control: 16.8 +/- 1.11%; MBF-NAME: 12.3 +/- 2.66%, p < 0.01). The proportion of cortical and medullary blood flow remains unaltered after chronic NO-synthase inhibition.


CONCLUSIONS
The nitric oxide plays an important role in determining the renal, cortical and medullary blood flow. The effect of EDRF in influencing the vascular resistance is more pronounced in the medulla than in the cortex.
Bartha
J
J
Department of Physiology, Semmelweis University of Medicine, Budapest, Hungary.
Vág
J
J
Hably
C
C
D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects*; D005260:Female; D007668:Kidney / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester