Endothelin (ET)-3 stimulates cyclic guanosine 3',5'-monophosphate production via ETB receptor by producing nitric oxide in isolated rat glomerulus, and in cultured rat mesangial cells.

Abstract

We investigated the effects of endothelins on receptor-me- diated cyclic nucleotide metabolism in rat glomerulus, inner medullary collecting duct (IMCD), and also in cultured rat glomerular mesangial cells. Endothelin (ET)-3 dose-depen- dently stimulated cGMP accumulation in glomerulus, which was higher than that of ET-1 or ET-2. ETB receptor agonist IRL 1620 produced cGMP in a dose-dependent manner, mim- icking the effect of ET-3. ETA receptor antagonist BQ123-Na did not inhibit ET-3-or IRL 1620-stimulated cGMP genera- tion. NG-monomethyl-L-arginine (L-NMMA) significantly in- hibited ET-3or IRL 1620-induced cGMP production, sug- gesting that ET-3-or IRL 1620-stimulated cGMP generation was mediated through nitric oxide (NO). Intracellular Ca chelator BAPTA /AM and calmodulin antagonist W-7, but not Ca channel blocker nicardipine, significantly inhibited ET-3-or IRL 1620-induced cGMP generation. In cultured rat mesan- gial cells, ET-3 stimulated cGMP generation through NO in the presence of fetal calf serum, which was not inhibited by addition of BQ123-Na. In IMCD, ET-3 had no stimulative ef- fect on cGMP generation. We conclude that ET-3 stimulates NO-induced cGMP generation through ETB receptor in glo- merulus. This effect seems to be mediated through intracellular Ca/calmodulin, but not through Ca influx via L-type Ca chan- nel. Mesangial cells can be a source of NO coupled to ETB receptor activation in glomerulus. From these results, mesan- gial ETB receptor may work to counteract the vasoconstrictive effect of endothelin caused via ETA receptor in glomerulus. (J. Clin. Invest. 1994 . 93:556-563.) Key words: microdissection. inner medullary collecting duct * endothelin receptor * Ca/ cal- modulin * protein kinase C 1. Abbreviations used in this paper: BAPTA/AM, bis-(o-aminopenoxy )-ethane-N,N,N',N'-tetraacetic acid, tetra( acetoxymethyl )-ester; BQl 23-Na, C31H41O7N6Na; DiC8, 1,2-dioctanoyl-sn-glycerol; EDRF, endothelium-derived relaxing factor; ET, endothelin; H-7, 1-(5-isoquinolinesulfonyl)-2