ROLE OF ENDOTHELIUM-DERIVED NITRIC-OXIDE IN CONTROL OF RENAL MICROVASCULATURE IN AGING MALE-RATS

The objective of this study was to evaluate the role of nitric oxide ( NO) in the regulation of whole kidney and glomerular hemodynamics duri ng aging. After 2 wk of oral treatment with N-nitro-L-arginine methyl ester (L-NAME; 4.5 mg.kg body wt-1.day-1) to inhibit NO synthesis, mal e rats, aged 3-5, 13-15, and 21-24 mo, were studied by micropuncture. Blood pressure increased by 50% in old (21-24 mo) rats with L-NAME but only 20-30% in the two younger groups. With L-NAME, renal vascular re sistance increased fivefold in old rats but only twofold in younger gr oups. Glomerular capillary pressure increased 20-30% in younger L-NAME rats and 60% in older rats. Afferent and efferent resistances increas ed dramatically, and the glomerular capillary ultrafiltration coeffici ent decreased in all L-NAME-treated rats but most strikingly in the 21 - to 24-mo-old group. Acute infusion of L-arginine significantly atten uated the effects of NO synthase inhibition on arterial pressure and r enal hemodynamics in both young and old rats. This study confirms that NO synthesis blockade has a greater effect on renal hemodynamics in a ging rats and implies that NO may play a progressively more important role in controlling renal function with advancing age.