The direct observation of arteriolar constriction induced by endothelin in vivo.

The effect of endothelin on the microvasculature of the hamster cheek pouch was observed directly using intravital microscopy. Endothelin caused a dose-dependent arteriolar constriction without affecting adjacent venules. Endothelin was less potent than vasopressin, but responses to endothelin were longer lasting (48.9 +/- 11.1% reduction in arteriolar diameter was still observed 30 min after topical application of 3 pmol endothelin). The results demonstrate that endothelin induces a prolonged increase in local arteriolar tone after a single application in vivo.