Eicosanoid production and levels of newly characterized eicosanoid‐forming enzymes in glomeruli and tubules of rat kidneys

Summary: We examined the production of prostaglandin (P0) E2, 6-keto PGF1α and thromboxane (Tx) B2, the mass of cyclooxygenase (COX) isoenzymes and the activities of phospholipases A2 and C in glomeruli, cortical tubules and medullary tubules of rat kidneys. Medullary tubules produced significantly greater amounts of PGE2, 6-keto PGF1α. and TxB2 than glomeruli or cortical tubules. the most abundant eicosanoid in medullary tubules was 6-keto PGF1α. By contrast, glomeruli and cortical tubules predominantly produced POE2 (glomeruli > cortical tubules). Levels of COX 1 were markedly greater in medullary tubules than in glomeruli or cortical tubules. Glomeruli had significantly greater amounts of COX 1 than cortical tubules. Detectable amounts of COX 2 were not present in the three preparations. the activity of phospholipase (PL) A2 against phosphatidyicholine (PC) was significantly greater in tubules (medullary tubules > cortical tubules) than in glomeruli. By contrast, there was a significant increase in the activity of PLA2 against phosphatidylethanolamine (PE) in glomeruli as compared to tubules (medullary tubules > cortical tubules). the activity of PLC was the Weatest in medullary tubules. Glomeruli had significantly greater activity of PLC than cortical tubules. the order of magnitude for the total activity of the three phospholipases in membranes was medullary tubules> glomeruli> cortical tubules. the total production rate of POE2, 6-keto PGF1α and TxB2 was in parallel with the amount of COX 1 and the total activity of membranous phospholipases A2 and C in the three preparations. In conclusion, there are differences in the production of PGE2, 6.-keto PGF1α and TxB2, the ainount of COX 1 and the activities of phospholipases A2 andC among glomeruli, cortical tubules and medullary tubules of rat kidneys; and the different aspects of COX 1 and phospholipases A2 and C have a key role in the control of eicosanoid production in the three preparations.