Figure 6.

Vasoconstrictor response of isolated and pressurized retinal arterioles to ET-1. (A) ET-1 elicited dose-dependent constriction of human retinal arterioles (resting diameter, 41 ± 8 μm; maximum diameter, 65 ± 7 μm; n = 5). (B) ET-1 (10 nM) caused comparable constriction of human (resting diameter, 33 ± 2 μm; maximum diameter, 58 ± 1 μm; n = 4) and porcine (resting diameter, 50 ± 4 μm; maximum diameter, 82 ± 4 μm; n = 4) retinal arterioles. Subsequent administration of H-1152 (10 μM) reversed the ET-1–induced constriction and reduced the myogenic tone of the vessels from both species by increasing the diameter toward maximum. Maximum diameter of vessels was established in Ca²⁺-free solution containing 0.1 mM sodium nitroprusside (Zero Ca²⁺). *P < 0.05 versus ET-1 alone.