Renal hemodynamics during pregnancy in chronically catheterized, conscious rats

Abstract

Two types of experiments were performed, cross-sectional and longitudinal. In the cross-sectional studies, rats were mated, later prepared surgically, and then 5 or more days after surgery, each examined twice during days 11 to 15 or days 18 to 20 of gestation. Nonpregnant rats matched for age and prepregnant weight served as controls. In the longitudinal studies, rats were catheterized and, starting 6 days later, examined twice; then the same rats were mated and each was studied on days 5, 8, 12, 16, and 20 of gestation, as well as on day 5 postpartum. In the cross-sectional studies, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were elevated by approximately 26% and 20%, respectively, above nonpregnant controls at 11 to 15 days of gestation (GFR, 2739 ± 94 vs. 2181 ± 134 μl.min-1, P<0.005; ERPF, 9367 ± 295 vs. 7785 ± 422 μl.min-1, P<0.01). By 18 to 20 days of gestation, GFR and ERPF had returned to levels that were not significantly different from nonpregnant values. The longitudinal studies confirmed these findings in every respect and further revealed that GFR and ERPF were elevated above nonpregnant values as early as day 5 of gestation (P<0.005). Thereafter, they rose to peak values, at 12 and 16 days of gestation, of 3122 ± 144 and 10,584 ± 541 μl.min-1, and then returned to nonpregnant levels by day 20 of gestation. Because these changes in GFR and ERPF resemble those of human pregnancy, the chronically prepared, conscious, pregnant rat can serve as a useful model in which to investigate the mechanisms underlying the changes.