Sex differences in renal hemodynamics in rats.

These studies were designed to investigate sex differences in renal hemodynamics under control conditions and in response to two different cyclooxygenase inhibitors. Studies were performed under anesthesia in males, females, and ovariectomized (OVX) rats and in separate groups of conscious, chronically catheterized male and female rats of a different strain. In the control periods, before cyclooxygenase inhibition, the male kidney was vasodilated relative to the female. Because male and female rats have the same number of glomeruli per kidney, the total vascular resistance per glomerulus is substantially greater in females than males. Cyclooxygenase inhibition in the anesthetized intact female rat produced significant increases in single-nephron glomerular filtration rate, glomerular plasma flow rate, glomerular filtration rate, and renal plasma flow, whereas afferent and efferent arteriolar resistances and renal vascular resistance fell. In contrast, anesthetized male and OVX female rats showed no renal hemodynamic response to cyclooxygenase inhibition. In the absence of anesthesia and recent surgery, intact awake female rats responded similarly to conscious male rats in that neither showed any response to cyclooxygenase inhibition. These data suggest a functional sex difference in both baseline renal hemodynamics and the renal response to cyclooxygenase inhibition, the latter unveiled by surgical stress.