Tissue variation of acute haemodynamic changes by NG-nitro-L-arginine in stroke-prone spontaneously hypertensive and Wistar-Kyoto rats.

1. The acute effects of nitric oxide synthase inhibition on the haemodynamics in stroke-prone spontaneously hypertensive (SHRSP) and normotensive Wistar-Kyoto (WKY) rats were investigated using radiolabelled microspheres. 2. Intravenous administration of 3 and 6 mg/kg NG-nitro-L-arginine (L-NNA) caused a significant increase in total peripheral resistance, a decrease in cardiac output and an increase in blood pressure in both SHRSP and WKY rats. 3. Significant decreases in regional blood flow (RBF) in the lung, muscle and stomach of WKY rats were observed following L-NNA administration. 4. NG-nitro-L-arginine produced a 70% increase in brain regional blood flow at a dose of 6 mg/kg only in SHRSP. 5. There was a variation in the involvement of nitric oxide (NO) in different tissues. 6. It is concluded that hypertension in SHRSP augments NO-mediated vasodilation.