EFFECTS OF PROSTAGLANDIN INHIBITION ON THE RENAL-FUNCTION CURVE DURING OVINE PREGNANCY

OBJECTIVE: This study was designed to assess the influence of prostagl andins on the steady-state relationship of mean arterial pressure and urinary sodium excretion. STUDY DESIGN: Ten nonpregnant and nine pregn ant ewes were chronically prepared with indwelling catheters and maint ained in metabolism cages. All the ewes received a continuous intraven ous infusion of indomethacin (5 mg/kg/day) for 24 days. Step increases in sodium intake (20, 100, 400, and 1200 mmol per day), each maintain ed for 6 days, were administered as a fixed dietary (20 mmol) componen t with the balance infused intravenously. Mean arterial pressure was c ontinuously monitored. The renal function curves were constructed from the steady-state mean arterial pressure-urinary sodium excretion rela tionships after sodium balance was attained. RESULTS: Indomethacin inh ibited urinary excretion of prostaglandin E(2) by 62% +/- 4% in nonpre gnant and 47% +/- 6% in pregnant ewes, and 6 keto-prostaglandin F-1 al pha, the stable metabolite of prostaglandin I-2, by 55% +/- 4% and 65% +/- 6% in nonpregnant and pregnant ewes, respectively. Blood volume w as not affected by indomethacin or salt in either group. Plasma angiot ensin II was suppressed less in pregnant ewes (60% vs 80%) by increase s in salt intake. Chronic treatment with indomethacin did not alter th e renal function curves of either nonpregnant or pregnant ewes. CONCLU SIONS: These results suggest that prostaglandins do not influence the steady-state relationship between mean arterial pressure and urinary s odium excretion in either nonpregnant or pregnant sheep.