Endothelin-1-induced contraction of bovine retinal small arteries is reversible and abolished by nitrendipine.
Endothelin-1 (porcine/human) induced a prompt, reversible, potent, concentration-dependent contraction of bovine isolated retinal small arteries (internal diameter, approximately 200 microns) with a concentration of endothelin-1 required to give half-maximal contraction of 2 x 10(-10) M. The maximal contraction induced by endothelin-1 was equal to 89% of the maximal contractile capacity. The vessel response to endothelin-1 was dependent on extracellular Ca2+. Withdrawal of extracellular Ca2+ or addition of nitrendipine, 10(-6) M, reduced the response of vessels contracted with 10(-9) M endothelin-1 by 80% and 75%, respectively. These results indicate that the endothelin-1-induced contraction of retinal arteries is dependent on an influx of extracellular Ca2+ through membrane potential-operated calcium channels. Endothelin-1, 10(-13)-10(-10) M, did not induce a relaxation of endothelium-intact arteries, indicating that endothelin-1 is incapable of releasing endothelium-derived relaxing factor in the retinal circulation. These results suggest that endothelin may participate in the regulation of retinal artery tone.
Nyborg
N C
NC
Department of Pharmacology, Aarhus University, Denmark.
Prieto
D
D
Benedito
S
S
Nielsen
P J
PJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D016232:Endothelins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009568:Nitrendipine / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D012161:Retinal Artery / Q000187:drug effects*
D016232:Endothelins; D009599:Nitroprusside; D009568:Nitrendipine; D000109:Acetylcholine; D002118:Calcium