Endothelium-dependent vasodilation in the uvea of hypertensive and normotensive rats

PURPOSE. The effects of endothelium-related substances such as acetylcholine, a stimulator of endogenous NO-production, the NO-synthesis inhibitor L-NMMA, the exogenous NO-donor sodium nitroprusside and the endothelin (ET) A -receptor antagonist BQ123, on uveal blood flow were investigated in normotensive and hypertensive SHR rats. METHOD. The radioactively-labelled microsphere method was applied for the measurement of regional blood flow in the uvea. RESULTS. Under resting conditions, local blood flow was lower in the hypertensive animals. The increase in choroidal blood flow (145 ± 50%; P < 0.01) and reduction in vascular resistance (-58 ± 7%; P < 0.01) observed in the WKY after IV infusion of acetylcholine, 2 µg × kg bw -1 × min -1, were significantly less pronounced in animals pretreated with L-NMMA, indicating local formation of NO as a vasodilator mechanism. In contrast, acetylcholine did not induce significant vasodilation in the choroid of SHR rats. In the anterior uvea of both strains, acet...