EFFECTS OF ENDOTHELIN-1 AND ENDOTHELIN-3 ON THE RELEASE OF PROSTANOIDS FROM ISOLATED PERFUSED RAT-KIDNEY

Endothelin-1 (ET-1) or endothelin-3 (ET-3) injected (0.1-100 pmol) into the renal artery of the isolated perfused rat kidney resulted in a dose-dependent increase in perfusion pressure (DELTA-PP). In this respect, ET-1 was 30 times more potent than ET-3. Infusion of ET-1 (3 nM) for 3 min induced a pronounced and long-lasting rise in DELTA-PP, in contrast to a transient increase in DELTA-PP after a 3-min infusion of ET-3 (10 nM). The pressor effect of endothelins was associated with the appearance of 6-keto-PGF1-alpha and PGE2 but not TXB2 in the perfusate. ET-1 produced a transient release of comparable amounts of prostacyclin and PGE2. In contrast to ET-1, ET-3 evoked a sustained release of prostacyclin and PGE2 at a ratio 3:1. It is assumed that PGE2 contributed to the vasoconstrictor responses of the endothelins in the rat kidney because indomethacin (5.6-mu-M) attenuated the pressor responses induced by ET-1 to a larger extent than that induced by ET-3. These results are in line with earlier observations that PGE2 is a vasoconstrictor in rat kidney. The differential release of prostanoids by ET-1 and ET-3 suggests the existence of separate receptors for ET-1 and ET-3 in the rat kidney. ET-3 appears to be a good candidate for an endogenous regulator of the release of prostacyclin.