Analysis of endothelin-1-induced contractions of guinea-pig trachea, pulmonary veins and different types of pulmonary arteries.

Endothelin-I (ET-I), a peptide produced by the vascular endothelium, has been found to produce strong and persistent contractions of various blood vessels. In the present study, the effects of ET-I were studied on isolated pulmonary arteries from four different levels (main pulmonary artery, large lobar arteries, small lobar arteries and intrasegmental arteries) of the guinea-pig. In addition, the effects of ET-I on pulmonary arteries were compared with those of pulmonary veins and trachea. ET-I elicited a strong concentration-dependent contraction of pulmonary arteries, veins and trachea. The effects of ET-I were more pronounced in pulmonary arteries than in corresponding veins. Significant regional variations within the pulmonary arterial system were disclosed. The tracheal segments showed the same sensitivity and the same degree of relative maximal contraction as the pulmonary veins. Although the cellular mechanisms behind the action of ET still are not clear, our results favour a direct action of ET-I on the vascular smooth muscle during vasoconstriction. Furthermore, the ET-I-induced contraction in guinea-pig lung seems to be independent of extracellular calcium.