Pregnant Rats With 5/6 Nephrectomy Have Normal Volume Expansion Despite Lower Renin and Kallikrein

To test the hypothesis that normal volume expansion during pregnancy is impaired during chronic renal failure, we evaluated the effects of 5/6 nephrectomy (Nx) in Sprague-Dawley rats. Partial Nx was produced by ligation of 2/3 renal arteries and contralateral Nx. Control rats had a sham operation. Four weeks later, rats were assigned to nonpregnant (n=6/each) or pregnant groups (n=11 to 12/each). At day 21, blood pressure, plasma volume, renal function, hormonal levels, and reproductive outcome were determined. Statistical analysis was performed by ANOVA, and values were expressed as mean±SEM. Rats with 5/6 Nx had proteinuria and lower creatinine clearance; pregnancy did not affect these parameters. Blood pressure increased in 5/6 Nx rats and was reduced by pregnancy. Both pregnant groups had lower hematocrit and higher plasma volume values (nonpregnant control, 13.4±0.2; nonpregnant 5/6 Nx, 14.4±0.2; pregnant control, 19.1±0.7, pregnant 5/6 Nx, 19±0.9 mL, P <0.001). Pregnancy increased plasma renin activity only in control rats (nonpregnant control, 2.0±0.7; nonpregnant 5/6 Nx, 1.6±1.1; pregnant control, 36.1±7.9, pregnant 5/6 Nx, 6.1±1.8 ng AI/mL per hour, P <0.001). Serum aldosterone levels were unaffected by 5/6 Nx and were higher in pregnant than in nonpregnant rats. Urinary kallikrein activity was reduced by 5/6 Nx and not changed by pregnancy (nonpregnant control, 1499±237; nonpregnant 5/6 Nx, 346±90; pregnant control, 1595±180, pregnant 5/6 Nx, 374±95 nmol/16 hours, P <0.001). No significant differences in fetal and placental weights were observed between control and 5/6 Nx rats. Present data indicate that 5/6 Nx pregnant rats were able to normally expand plasma volume despite lower renin and kallikrein levels.