Endothelin inhibits thick ascending limb chloride flux via ETBreceptor-mediated NO release

• DOI: 10.1152/ajprenal.2000.279.2.f326
• Publication Date: 2017-12-23T12:44:35Z
• Authors: Craig F. Plato; David M. Pollock; Jeffrey L. Garvin
• Keywords: Male; Receptors, Endothelin; Endothelins; In Vitro Techniques; Nitric Oxide; Receptor, Endothelin B; Absorption; Rats; Rats, Sprague-Dawley; 03 medical and health sciences; 0302 clinical medicine; Chlorides; Loop of Henle; Animals

Endothelin-1 (ET-1) inhibits transport in various nephron segments, and the thick ascending limb of the loop of Henle (TALH) expresses ET-1 receptors. In many tissues, activation of ETBreceptors stimulates release of NO, and we recently reported that endogenous NO inhibits TALH chloride flux ( JCl). However, the relationship between ET-1 and NO in the control of nephron transport has not been extensively studied. We hypothesized that ET-1 decreases NaCl transport by cortical TALHs through activation of ETBreceptors and release of NO. Exogenous ET-1 (1 nM) decreased JClfrom 118.3 ± 15.0 to 62.7 ± 13.6 pmol · mm−1· min−1(48.3 ± 8.2% reduction), whereas removal of ET-1 increased JClin a separate group of tubules from 87.6 ± 10.7 to 115.2 ± 10.3 pmol · mm−1· min−1(34.5 ± 6.2% increase). To determine whether NO mediates the inhibitory effects of ET-1 on JCl, we examined the effect of inhibiting of NO synthase (NOS) with NG-nitro-l-arginine methyl ester (l-NAME) on ET-1-induced changes in JCl. l-NAME (5 mM) completely prevented the ET-1-induced reduction in JCl, whereas d-NAME did not. l-NAME alone had no effect on JCl. These data suggest that the effects of ET-1 are mediated by NO. Blockade of ETBreceptors with BQ-788 prevented the inhibitory effects of 1 nM ET-1. Activation of ETBreceptors with sarafotoxin S6c mimicked the inhibitory effect of ET-1 on JCl(from 120.7 ± 12.6 to 75.4 ± 13.3 pmol · mm−1· min−1). In contrast, ETAreceptor antagonism with BQ-610 did not prevent ET-1-mediated inhibition of TALH JCl(from 96.5 ± 10.4 to 69.5 ± 8.6 pmol · mm−1· min−1). Endothelin increased intracellular calcium from 96.9 ± 14.0 to 191.4 ± 11.9 nM, an increase of 110.8 ± 26.1%. We conclude that exogenous endothelin indirectly decreases TALH JClby activating ETBreceptors, increasing intracellular calcium concentration, and stimulating NO release. These data suggest that endothelin acts as a physiological regulator of TALH NO synthesis, thus inhibiting chloride transport and contributing to the natriuretic effects of ET-1 observed in vivo.