AGE-RELATED-CHANGES IN RENAL HEMODYNAMICS IN FEMALE RATS - ROLE OF MULTIPLE PREGNANCY AND NO

The objective of the present study was to evaluate 1) the effect of mu ltiple pregnancy and aging on renal function and 2) the effect of NO i nhibition on renal function in aged virgin and multiply pregnant rats. Renal hemodynamics were measured in the presence or absence of chroni c (2 wk) NO synthase inhibition (nitro-L-arginine methyl ester, L-NAME ) in young virgins (YV, 3-4 mo), old virgins (OV, 17-18 mo), and old r etired breeders (ORE, 17-18 mo) that had sustained eight to nine pregn ancies and lactations. Blood pressure was not different between contro l YV and OV. Glomerular filtration rate (GFR), renal plasma flow (RPF) , and renal vascular resistance (RVR) were similar in OV and control Y V. In contrast, the renal vasculature of ORE was more vasoconstricted in ORE than in YV or OV: GFR was decreased by 35% and RVR was higher t han in YV or OV. With L-NAME there were similar increases in arterial pressure in all rats. In control YV, L-NAME had no effect on GFR, decr eased RPF by 20%, and increased RVR by twofold. In OV, L-NAME decrease d GFR by 30% and RPF by 60% and increased RVR by 3.3-fold. In ORE, L-N AME had no effect on GFR, decreased RPF by 30%, and increased RVR by 1 .8-fold. These data suggest that the renal vasculature of ORE is vasoc onstricted and that the mechanism may be due to a decrease in NO produ ction.