EFFECTS OF INHIBITION OF NITRIC-OXIDE SYNTHASE ON SYSTEMIC ARTERIAL-PRESSURE AND RENAL VASCULAR-RESISTANCE IN CATS

These studies were undertaken to examine the systemic and renal effects of the pharmacological inhibition of endothelium-derived nitric oxide (EDNO) in cats. In six healthy cats, the intravenous infusion of nitro-L-arginine at a dose of 100 mug kg-1 bodyweight min-1 resulted in a marked increase (P<0.001) in mean arterial pressure from the control value of 116.7 +/- 4.6 mmHg to 154.2 +/- 6.8 mmHg and an increase (P<0.05) in renal vascular resistance from the control value of 3.69 +/- 0.33 mmHg min ml-1 to 6.83 +/- 1.15 mmHg min ml-1. The increase in renal vascular resistance was generalised, with comparable increments in preglomerular and postglomerular vascular resistance. Mean values for glomerular capillary pressure (61.1 +/- 1.9 vs 61.9 +/- 1.6 mmHg), calculated from the sum of arterial colloid osmotic pressure plus proximal tubule stop-flow pressure, did not change in response to the infusion of nitro-L-arginine. However, there was a marked reduction in renal blood flow (29.4 +/- 3.1 to 16.9 +/- 2.3 ml min-1, P<0.01) and glomerular filtration rate (5.22 +/- 0.57 to 3.52 +/- 0.45 ml min-1, P<0.01). These results provide evidence that EDNO plays an important role in the basal regulation of systemic arterial blood pressure and renal haemodynamics in cats.