Endothelins.

The endothelins (ETs) are a family of newly discovered peptides with potent vasoconstrictor properties. They were first discovered in cultured endothelial cells but ET expression has since been found in many other tissues such as brain and kidney. They are peptides with 21 amino acids formed by hydrolytic cleavage of a larger peptide, big ET. Release of ETs from cultured endothelial cells is modulated by a variety of chemical and physical stimuli and as no storage sites have been identified it is suggested that endothelin release is regulated at the level of transcription or translation. Both big ET and ET-1 are found circulating in the blood. The levels are elevated in shock, myocardial infarction and kidney failure indicative of enhanced formation in these diseases. The literature now abounds with reports on actions of the ETs in vitro and in vivo. The vasoconstrictor properties are powerful and long-lasting. Several studies also show a mitogenic effect, indicating a possible trophic role. It is likely that in the next few years the development of inhibitors of endothelin synthesis and/or action will be of importance in unravelling the role of the ETs.