A peptide precursor of endothelin-1
Big endothelin-1 (BET-1) (1-38) is a peptide precursor of endothelin-1 produced by vascular smooth muscle and endothelium. BET-1 is converted to endothelin-1 by endothelin-converting enzyme (ECE) and to endothelin-1 (1-31) by chymase. It is also converted to endothelin-1 (1-32) by matrix metalloproteinase-2 (MMP-2). BET-1 (50 pmol) induces vasoconstriction in isolated rat mesenteric arteries, an effect that is blocked by the MMP-2 antagonist TIMP-2. In vivo, BET-1 (0.1-10 nmol/kg, i.v.) dose-dependently increases blood pressure and bradycardia and leads to renal and hindquarter vasoconstriction in rats as well as abdominal constriction in mice (ED50 = 0.043 mg/kg), effects that are reversed or prevented by the ECE inhibitor phosphoramidon . It also induces mesenteric vasoconstriction in rats. Unlike endothelin-1, BET-1 (100 pmol/kg, i.v.) increases water and sodium excretion in rats independent of the endothelin A receptor.
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