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 multiple pregnancy and aging on renal function and 2) the effect of NO inhibition on renal function in aged virgin and multiply pregnant rats. Renal hemodynamics were measured in the presence or absence of chronic (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 retired breeders (ORB, 17-18 mo) that had sustained eight to nine pregnancies and lactations. Blood pressure was not different between control YV and OV. Glomerular filtration rate (GFR), renal plasma flow (RPF), and renal vascular resistance (RVR) were similar in OV and control YV. In contrast, the renal vasculature of ORB was more vasoconstricted in ORB than in YV or OV:GFR was decreased by 35% and RVR was higher than 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, decreased RPF by 20%, and increased RVR by twofold. In OV, L-NAME decreased GFR by 30% and RPF by 60% and increased RVR by 3.3-fold. In ORB, L-NAME had no effect on GFR, decreased RPF by 30%, and increased RVR by 1.8-fold. These data suggest that the renal vasculature of ORB is vasoconstricted and that the mechanism may be due to a decrease in NO production.