Gender differences in the altered renal excretory response to an acute volume expansion in rats with low glomerular number

Abstract

In recent study we found that treatment with an Ang II AT1 receptor antagonist (ARA) during nephrogenic period reduces nephron number in males and females but the subsequent renal structural changes are greater in males. The aim was to evaluate whether there are gender differences in the excretory response to an acute volume expansion (AVE) in rats with a decreased nephron number, and whether these differences are enhanced during aging. Newborn SD rats were treated with vehicle or an ARA (L-158.809, 7 mg/kg/day) during the first 14 postnatal days and the renal response to an AVE examined at three and nine months of age in control (CO) and ARA treated males and females. Arterial pressure and renal hemodynamics did not change in any group during the AVE. At three months of age, AVE-induced increments in sodium excretion and urine flow rate were greater in vehicle treated males (101 ± 4 μEq/min/bw and 620 ± 3 μl/min/bw) than in ARA treated males (54 ± 3 μEq/min/bw and 360 ± 4 μl/min/bw). Reduction in the renal response to AVE was similar in ARA treated males and females. Renal excretory ability to eliminate the AVE only was affected by age in ARA treated males. Natriuresis and diuresis decreased by 33% and 40%, respectively, in this group at nine vs. three months of age. The results of this study suggest that the renal excretory ability to eliminate an AVE is impaired when nephron number is reduced, and only aggravated by aging in males.