Thromboxane B2 and prostaglandin E2 in the K+-depleted rat kidney

There is a considerable amount of interest in prostaglandin E2 (PGE2) metabolism in potassium depletion, but the findings remain inconclusive. Thromboxane A2 (TXA2) is another type of prostaglandin with a vasoconstrictive property and its biosynthesis in the kidney is altered under pathophysiological conditions. We investigated the production of both immunoassayable PGE2 and thromboxane B2 (TXB2), a chemically stable metabolite of TXA2, in the chronically K+-depleted rat kidney. During a 90-min in vitro incubation of papillary slices obtained from K+-depleted rats, TXB2 production was increased, but PGE2 biosynthesis was decreased and PGF2 alpha remained unaltered compared with control rats. In the cortex, TXB2 production was low, but it was greater in K+-depleted rats compared with control rats. Deletion of K+ from the incubation medium had no measurable effect on either TXB2 or PGE2 production in both K+-depleted and control rats. Formation of [14C]TXB2 from [14C]PGH2 by microsomes from renal papilla was greater in K+-depleted rats compared with control rats, suggesting that the increased TXB2 production in the K+-depleted rat kidney is probably due to an activation of TXA2 synthetase.