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(Hypertension. 2004;44:334.)
© 2004 American Heart Association, Inc.

Scientific Contributions

Renal and Hormonal Effects of Water Deprivation in Late-Term Pregnant Rats

From the Center for Medical Research (S.P.S., A.G.) and Department of Obstetrics and Gynecology (S.P.S.), School of Medicine; and Department of Physiology (C.P.V.), Faculty of Biological Sciences, Pontificia Universidad Católica de Chile.

Correspondence to Dr Sofía P. Salas, Center for Medical Research, School of Medicine, Pontificia Universidad Católica de Chile, PO Box 114-D, Santiago, Chile. E-mail ssalas{at}med.puc.cl

Water-retaining hormones are stimulated during pregnancy allowing normal volume expansion. Because pregnant rats actively retain water, we postulate that water deprivation (WD) would cause a greater reduction in plasma volume in pregnant than in nonpregnant rats. To test this hypothesis, Sprague-Dawley pregnant and nonpregnant rats were water-deprived for 48 hours. At day 19 of pregnancy, or in the corresponding day in nonpregnant rats, they were randomly assigned to either a WD or a control (C) pair-fed group (n=10 to 12 per group). WD significantly reduced body weight, food intake, and creatinine clearance, and increased urinary osmolality in nonpregnant and pregnant rats. WD reduced plasma volume in a similar proportion in nonpregnant and pregnant rats (nonpregnant rats C=13.1±0.4, WD=11.0±0.2; pregnant rats C=19.4±0.7, WD=16.8±0.5 mL, P<0.001). Both groups of pregnant rats had a similar reduction in blood pressure. Plasma renin activity (nonpregnant rats C=6.1±1.1, WD=20.5±2.0; pregnant rats C=49±9.7, WD=94±12 ng angiotensin I/mL per hour, P<0.001) and plasma aldosterone levels were increased by pregnancy and further increased by WD. WD significantly reduced urinary kallikrein. WD caused a significant reduction in fetal but not placental weights. Present data indicate that 48-hour WD reduced renal kallikrein and further stimulated water-retaining hormones. We speculate that these are compensatory changes contributing to the maintenance of pregnancy in response to WD.

Key Words: preeclampsia • pregnancy • renin • bradykinin • aldosterone • kallikrein • mineralcorticoids