SEX-DIFFERENCES IN CONTROL OF RENAL OUTER MEDULLARY CIRCULATION IN RATS - ROLE OF PROSTAGLANDINS

A calibration technique was developed to quantify blood flow changes i n the renal cortex and outer medulla in rats using platinum needle ele ctrodes sensing partial pressure of locally generated hydrogen. Measur ements were made in male and female rats to investigate sex difference s in the humoral control and autoregulation of regional renal circulat ions. In males, both cortical and outer medullary blood flows were eff iciently auto-regulated above an arterial pressure of 100 mmHg. The co nverting-enzyme inhibitor quinapril increased blood flow by 20% in bot h kidney zones, and inhibition of prostaglandin synthesis by indometha cin did not change the flow. In females, similar results were obtained only for the cortex; the medulla had a different response pattern. Th e blood flow was not autoregulated in the experimental pressure range up to 120 mmHg; quinapril did not change the flow, but indomethacin de creased the flow by 16% and at the same time restored its autoregulati on capacity. We conclude that 1) the medulla of female rats has a high basal level of vasodilator prostaglandins, which interferes with bloo d flow autoregulation in this kidney area, and 2) medullary flow in fe male rats is little affected by endogenous angiotensin.