Expression of endothelins 1 and 3 in the rat kidney

Endothelins (ETs) 1 and 3 are expressed in the rat kidney, but the factors that regulate this expression remain unknown. To try to understand what these might be, we have measured the renal levels of ET-1 and ET-3 mRNAs by the ribonuclease protection-assay technique after a number of clearly defined renal/hemodynamic insults. 1) Six hours after the induction of hemorrhagic anemia and hypotension, there was a threefold increase in ET-1 mRNA and a simultaneous threefold decrease in ET-3 mRNA. This indicates that, in this situation, these two ET isoforms are differentially controlled and emphasizes the need for assay techniques capable of distinguishing between them. 2) One day after application of a 0.2-mm clip to the left renal artery, there was a > 2.5-fold induction of ET-1 mRNA in that kidney, which persisted for 10 days. A smaller rise in ET-1 mRNA was seen in the contralateral organ. After 2 days, ET-3 mRNA levels were reduced by approximately 50% in the clipped organ. Both ramipril (an angiotensin-converting enzyme inhibitor, 7.5 mg/kg daily) and bosentan (a nonselective ET receptor antagonist, 100 mg/kg daily) substantially reduced the elevation in ET-1 mRNA seen in the clipped kidney after 2 days, suggesting that the generation of angiotensin II and the action of ET itself are involved in the mechanism by which clipping stimulates ET-1 expression. By contrast, ramipril, but not bosentan, prevented the reduction in ET-3 mRNA levels. 3) Renal denervation, dietary salt restriction, or diuretic treatment (furosemide) did not alter renal expression of ET-1 or ET-3.(ABSTRACT TRUNCATED AT 250 WORDS)