Endothelin‐1 and Endothelin‐3 Regulate Endothelin Receptor Expression in Rat Coronary Arteries

E-ISSN： 1742-7843|117|5|297-305

ISSN： 1742-7835

Source： BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY (ELECTRONIC), Vol.117, Iss.5, 2015-11, pp. : 297-305

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Abstract

AbstractIn ischaemic hearts, endothelin (ET) levels are increased, and vasoconstrictor responses to ET‐1 are greatly enhanced. We previously reported that ETB receptors are up‐regulated in the smooth muscle layer of coronary arteries after myocardial ischaemia–reperfusion and that the MEK–ERK1/2 signalling pathway is involved in ETB receptor up‐regulation. Whether ETs are directly involved in receptor regulation has not been determined. We suggest that ET‐1 and ET‐3 alter the expression/activity of ET receptors in coronary vascular smooth muscle cells. Vasoconstrictor responses were studied in endothelium‐denuded coronary artery segments from rats that were subjected to experimental ischaemia–reperfusion or in organ‐cultured segments. Post‐ischaemic and cultured coronary arteries exhibited similar increased sensitivity to ET‐3. ETA receptor‐mediated vasoconstriction was dominant in fresh and non‐ischaemic arteries. Organ culture significantly up‐regulated ETB receptors and down‐regulated ETA receptor expression. Co‐incubation with ET‐1 (1 nM) or ET‐3 (100 nM) induced further down‐regulation of the ETA receptor mRNA, while the function and protein level of ETA remained unchanged. ET‐3 (100 nM) further up‐regulated ETB receptor mRNA and proteins but abolished ETB receptor‐mediated vasoconstriction, suggesting a desensitization of ETB receptors that was not observed with ET‐3 (1 nM). In conclusion, ET‐1, which is the most prevalent isoform in the cardiovascular system, induces down‐regulation of ETA receptor expression without changing ETA or ETB receptor function or protein levels. Intermediate concentrations of ET‐3 had an effect that was similar to that of ET‐1, such that high concentrations of ET‐3 (100 nM) up‐regulated the ETB receptor at the gene and protein levels but switched off the function of the ETB receptors via desensitization.