Pharmacological evidence that flow- and potassium-induced contraction of rabbit facial vein may involve the same calcium entry pathway.
Flow-induced contraction depends upon extracellular Ca++, but the underlying Ca++ entry pathway involved is unknown. We chose the rabbit facial vein to carry out this study because, in addition to contracting to a number of pharmacological agents and developing myogenic tone in response to stretch in vitro, flow-induced contraction also can be consistently demonstrated. Our goal was to determined whether the Ca++ entry pathway for flow-induced contraction could be distinguished from that involved in K(+)-, histamine- and stretch-induced contraction through the use of a Ca++ entry activator: Bay K 8644 and the Ca++ entry blockers nifedipine, diltiazem and verapamil and also cobalt and manganese. All four types of contractions studied are dependent on extracellular Ca++ Flow- and K(+)-induced contraction were equally sensitive to inhibition by nifedipine, verapamil and diltiazem. Those to histamine and stretch were not. Furthermore, the flow- and K(+)-induced contractions were enhanced equivalently by the calcium channel activator, Bay K 8644, but to a lesser degree than those to histamine and stretch. The inorganic calcium channel blockers, Co++ and Mn++ effected equally flow-, K(+)- and histamine-induced contraction. They were more potent in their inhibition of stretch-induced contraction. Our results suggest that flow- and K(+)-induced contractions depend on a similar Ca++ entry system into vascular smooth muscle: probably a voltage-gated Ca++ entry pathway, which is different from that utilized by histamine and stretch.
Xiao
X H
XH
Department of Pharmacology, University of Vermont, College of Medicine, Burlington.
Bevan
J A
JA
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005145:Face / Q000098:blood supply*; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D011188:Potassium / Q000494:pharmacology*; D011817:Rabbits; D012039:Regional Blood Flow / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014680:Veins
D002121:Calcium Channel Blockers; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D006632:Histamine; D011188:Potassium; D002118:Calcium