Endothelin-induced vasoconstriction of small resistance vessels in the microcirculation of the rat cremaster muscle.

Recently, a peptide (endothelin) which has been shown to have potent vasoconstrictor properties has been isolated from the vascular endothelium. In the present study, we assessed the responsiveness of small arterioles and venules in the rat cremaster muscle to topical application of endothelin using closed-circuit television microscopy. Exposure to increasing concentrations of endothelin (10(-15)-10(-7) M) produced a dose-dependent constriction in large (90 +/- 8 microns), intermediate (50 +/- 6 microns), and small (21 +/- 4) arterioles. Large (144 +/- 17 microns) and intermediate (79 +/- 18 microns) venules also constricted to the peptide, but the responses were inconsistent and smaller in magnitude. The constriction to endothelin was long lasting and resistant to washout. Arteriolar reactivity to endothelin was similar for all vessel levels with ED50 values ranging from 10(-9) to 10-s;1(0) M. Exposure to the calcium entry blocker, verapamil, attenuated the endothelin-induced constriction in 3A arterioles, suggesting that the constriction in skeletal muscle arterioles is at least partially due to the increased entry of extracellular calcium.