Heterozygous Knock-Out of ET B Receptors Induces BQ-123–Sensitive Hypertension in the Mouse

Publisher Website
Google Scholar
Abstract
—Homozygous knock-out of ET A or ET B receptor genes results in lethal developmental phenotypes in the mouse. Such deleterious phenotypes do not occur in heterozygous littermates. However, it remains to be determined whether mice partially defective in ET A or ET B receptors display significant alterations in their responses to exogenous or endogenous endothelin-1 (ET-1). Furthermore, the anesthetized ET B (+/−) knock-out mice showed a significantly higher mean arterial blood pressure than the ET A (+/−) knock-out or their wild-type littermates. The pressor response to ET-1 but not to a selective ET B agonist, IRL-1620, was significantly reduced in the ET A (+/−) knock-out mice. In ET B (+/−) knock-out mice, the pressor effect of IRL-1620 was more markedly altered than those induced by ET-1. In wild-type mice, both ET A and ET B receptors were found to be involved in the pressor effect of ET-1, as confirmed by the significant and specific antagonism induced by either BQ-123 (ET A antagonist) or BQ-788 (ET B antagonist). Also, ET A -selective or mixed ET A /ET B - but not ET B -selective antagonists reversed the hypertensive state of the ET B (+/−) knock-out mice to the level of wild-type littermates. Finally, radiolabeled ET-1 plasmatic clearance was altered in ET B (+/−) but not ET A (+/−) knock-out mice when compared with wild-type animals. Thus, heterozygous knock-out of ET B receptors results in a hypertensive state, suggesting an important physiological role for that particular receptorial entity in opposing the endogenous ET-1–dependent pressor effects in the mouse.