The effect of the thromboxane A2 synthesis inhibitor OKY-046 on renal function in rabbits following release of unilateral ureteral obstruction.

A marked decrease in renal blood flow (RBF) and glomerular filtration rate (GFR) was found after 24, 48 and 72 hours of total unilateral ureteral obstruction (UUO) in the rabbit. Contralateral GFR showed a modest increase consistent with compensatory hypertrophy. The urinary excretion of thromboxane B2 (TxB2), the stable metabolite of the vasoconstrictor prostaglandin, thromboxane A2 (TxA2) was significantly elevated in the urine obtained following release of the obstructed ureter when compared to the TxB2 level in the urine from the contralateral kidney. Continuous infusion of OKY-046 at 100 micrograms./kg./min. over 24 hours during UUO decreased TxB2 excretion by greater than 80 per cent. However there was no significant preservation of RBF or GFR of the obstructed kidney following ureteral release despite the selective inhibition of TxA2. Moreover the increase in contralateral GFR was also abolished. Taken together with other studies these results strongly suggest that the potent vasoconstrictor TxA2 is not responsible for the rise in renal resistance that follows acute UUO.