The endothelin family: an overview.

Endothelin (ET) is a potent vasoconstrictive peptide initially found in the conditioned medium of cultured endothelial cells (1). It comprises 21 amino acid residues including four cysteine residues. The four cysteine residues form two intramolecular disulfide bonds. No amino acid sequence similar to that of ET had been previously reported. Furthermore its pharmacological action was unique. When it was injected intravenously into rats, a sustained and long-lasting pressor response was observed, suggesting a role of ET in maintenance of blood pressure or generation of hypertension. For these reasons many investigators were interested in this peptide. However, numerous reports following publication of the first paper detailing study of ET revealed that the mechanism for maintenance of blood pressure was not so simple. Apart from this problem, many pharmacological studies revealed that ET was active not only in the cardiovascular system but also in noncardiovascular systems. Those results stimulated further the worldwide interest in ET.