Antihypertensive Effects of a Novel Endothelin-A Receptor Antagonist in Rats

Abstract

Abstract Endothelin is a potent pressor agent mediated primarily through activation of endothelin-A receptors on vascular smooth muscle. Surprisingly, there is no consensus in the literature regarding the role of endothelin itself or endothelin-A receptors in hypertension. The goal of this study was to compare the effects of the novel, selective endothelin-A receptor antagonist BMS-182874 in various models of hypertension. BMS-182874 specifically inhibited the pressor response to endothelin-1 (0.3 nmol/kg IV) in Sprague-Dawley rats in a dose-dependent manner (ED 25 =8 μmol/kg IV) but had no effect on changes in mean arterial pressure brought about by other vasoactive agents. The antihypertensive effects of BMS-182874 were evaluated in conscious deoxycorticosterone acetate (DOCA)–salt hypertensive rats, spontaneously hypertensive rats (SHR), and sodium-deplete SHR. BMS-182874 reduced blood pressure in DOCA-salt hypertensive rats when administered at a dose of 30, 100, or 300 μmol/kg IV. A maximal decrease of approximately 45 mm Hg was observed after treatment with 100 μmol/kg IV. Three days of oral or intravenous treatment with BMS-182874 (100 μmol/kg) elicited a sustained decrease in blood pressure in the DOCA-salt hypertensive rats. In SHR, BMS-182874 decreased blood pressure by approximately 30 mm Hg, but the antihypertensive effects were similar at doses of 75, 150, and 450 μmol/kg PO. In sodium-deplete SHR, BMS-182874 did not significantly reduce blood pressure. In summary, BMS-182874 is a specific, orally active endothelin-A receptor antagonist that is efficacious in mineralocorticoid hypertension in rats but has less effect in sodium-replete and sodium-deplete SHR. Thus, endothelin-A receptor activation may play a role in volume-dependent or low-renin hypertension but is unlikely to be important in all hypertensive states.