The very potent endogenous vasoconstrictor endothelin was discovered in 1988. We know now that there are three
isoforms (1, 2, and 3) and two receptor subtypes (A and B). A whole range of peptide and non-peptide antagonists has
been developed, some selective for A or B receptors and others with non-selective A/B antagonistic activity. So far the
main application of these agents has been experimental—ie, endothelin blockers are used to throw light on disease
mechanisms, most notably cardiovascular and renal. However, the non-selective antagonist bosentan and a few other
agents have been studied clinically. Evidence so far from preclinical studies and healthy volunteers and from the
limited number of investigations in patients permits a listing of the potential areas of clinical interest. These are mainly
cardiovascular (eg, hypertension, cerebrovascular damage, and possibly heart failure) and renal. Clouds on the horizon
are the need to show that these new agents are better than existing drugs; the possibility of conflicting actions if
mixed A/B antagonists are used; and animal evidence hinting that endothelin blockade during development could be
dangerous.