EFFECT OF INDOMETHACIN ON BLOOD-PRESSURE IN THE NORMOTENSIVE UNANESTHETIZED RABBIT - POSSIBLE RELATION TO PROSTAGLANDIN SYNTHESIS INHIBITION

To test whether endogenous prostaglandins contribute to regulation of blood pressure, the effect of an inhibitor of prostaglandin synthesis, indomethacin, on mean aortic blood pressure in the normotensive, unanesthetized rabbit was studied. Daily administration of indomethacin at 42 .mu.mol/kg s.c., but not of vehicle only, for 14 consecutive days, elevated the average mean arterial pressure in 7 rabbits from 88 .+-. 3 mmHg on the last day of the control period to 105 .+-. 3 mmHg (P < 0.01) and 107 .+-. 2 mmHg (P < 0.01) on days 6 and 14 of indomethacin treatment, respectively, and reduced urinary excretion of prostaglandin-like substance from 1.06 .+-. 0.26 to 0.17 .+-. 0.05 nmol of prostaglandin E2 equivalents/day (P < 0.05; no. = 5). Neither indomethacin nor the vehicle affected intake of water, 24-h urine volume, cumulative difference between Na intake and urinary Na excretion or plasma volume. Apparently, 1 or more prostaglandins contribute to maintain normotension in the rabbit; reduction in prostaglandin biosynthesis may cause blood pressure to rise.