Characteristics of myogenic tone in the rat ophthalmic artery.
The pressure-induced constriction in the rat ophthalmic artery was characterized. Ophthalmic arteries were isolated, cannulated in an arteriograph, and pressurized. Arteries developed 25% constriction at 70 mmHg of intraluminal pressure. Arteries maintained almost similar diameter over the range of pressures 50-210 mmHg, and forced dilatation was observed at pressures >210 mmHg. Denudation of endothelium increased the sensitivity of arteries to pressure-induced constriction, and significantly higher myogenic tone was observed in the pressure range of 10-100 mmHg. Indomethacin and cyclooxygenase-2 inhibition by SC-236 decreased myogenic tone, whereas cyclooxygenase-1 inhibition by SC-560 potentiated myogenic tone in a lower concentration range and decreased at a higher concentration. Pressure-induced constriction was completely blocked by 1 microM nifedipine. Phospholipase C inhibition by 6 microM U-73122 decreased myogenic tone by 39%, whereas PKC inhibitor GF-109203X (3 microM) had no effect. Constriction to phenylephrine was significantly decreased by U-73122 (1 microM) and GF-109203X (3 microM) at an intraluminal pressure of 10 mmHg. Rho-kinase inhibition by Y-27632 (30 microM) and HA-1077 (30 microM) decreased myogenic tone by 75% and 73%, respectively, and 1 microM Y-27632 significantly decreased myogenic tone developed in response to graded increases in pressure. These results suggest that rat ophthalmic artery has an efficient pressure-dependent autoregulatory function that is modulated by endothelium. Contribution of phospholipase C-activation to myogenic tone is minimal, whereas Rho-kinase activation plays a predominant role in the myogenic reactivity in this artery.
Ito
Isamu
I
Wake Forest Institute of Regenerative Medicine, Wake Forest Univ. Baptist Medical Hospital, Medical Center Blvd., Winston-Salem, NC 27157, USA.
Jarajapu
Yagna P R
YP
Grant
Maria B
MB
Knot
Harm J
HJ
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D006487:Hemostasis / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009880:Ophthalmic Artery / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000502:physiology*