Activation of endothelin ETB receptors increases glomerular cGMP via an L-arginine-dependent pathway.
The effects of endothelins (ET) on guanosine 3',5'-cyclic monophosphate (cGMP) levels in intact rat glomeruli were examined. ET-3 produced a rapid approximately fivefold increase in cGMP levels with the maximum effect occurring at 1 min. The ET-3-induced increase in cGMP accumulation occurred in the absence and presence of 3-isobutyl-1-methylxanthine. ET-1, ET-2, ET-3, and the structurally related toxin, sarafotoxin S6c, all increased glomerular cGMP levels in a concentration-dependent manner and with similar potencies (EC50 approximately 15-30 nM). The L-arginine analogue, N omega-nitro-L-arginine (L-NNA), reduced basal levels of cGMP and also totally inhibited ET-induced increases in cGMP as did methylene blue, an inhibitor of soluble guanylate cyclase. The effect of L-NNA was attenuated by L-arginine but not by D-arginine. The stimulation of cGMP accumulation by ET-3 was dependent on extracellular Ca2+ and was additive to atriopeptin III but not to acetylcholine. The ETA-selective antagonist, BQ 123, had no effect on ET-3-induced formation of cGMP. Glomerular membranes displayed high-affinity (Kd = 130-150 pM) and high-density (approximately 2.0 pmol/mg) binding sites for 125I-ET-1 and 125I-ET-3. ET-1, ET-3, and sarafotoxin S6c displaced 125I-ET-1 binding to glomerular membranes with similar affinities. BQ 123 had no effect on 125I-ET-1 binding. We conclude that ET increases cGMP levels in glomeruli by stimulating the formation of a nitric oxide-like factor that activates soluble guanylate cyclase. This effect of ET appears to be mediated by activation of ETB receptors and may serve to modulate the contractile effects of ET.
Edwards
R M
RM
Department of Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406.
Pullen
M
M
Nambi
P
P
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D001667:Binding, Competitive; D006152:Cyclic GMP / Q000378:metabolism*; D016232:Endothelins / Q000494:pharmacology; D007678:Kidney Glomerulus / Q000378:metabolism*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester; D010446:Peptide Fragments; D010456:Peptides, Cyclic / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000502:physiology*
D016232:Endothelins; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; C062525:atrial natriuretic factor prohormone (103-126); D009320:Atrial Natriuretic Factor; D001120:Arginine; D006152:Cyclic GMP; D000109:Acetylcholine; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D019331:NG-Nitroarginine Methyl Ester