Potentiation of stretch-induced myogenic tone of dog cerebral artery by hemolysate and the inhibitory action of calcium antagonists.
Quick stretching of a helical strip of dog basilar artery at a rate of 10 cm/s to 140% of the slack length of the muscle evoked a delayed contraction. A small amount of hemolysate (0.01-0.2 mg/ml as hemoglobin), which increased the basal tone by 10-15% of the maximum contracture produced by 80 mM K+, potentiated the stretch-induced contraction 2- to 3-fold over the control. The enhanced response to stretch was attenuated by removal of the endothelium and was readily suppressed by Ca2+ antagonists such as nisoldipine and other dihydropyridine drugs as well as diltiazem. The hemolysate had no apparent effect on the contraction due to a quick stretch in Ca2+-free medium or on the contractile response of a chemically skinned arterial strip in the relaxing solution. The results suggest that the hemolysate potentiates the contractile response to stretch by promoting the transmembrane supply of Ca2+. The presence of endothelium seems to amplify the vasoconstrictor action of the hemolysate.
Nakayama
K
K
Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Japan.
Tanaka
Y
Y
Fujishima
K
K
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D001790:Blood Physiological Phenomena; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002536:Cerebral Arteries / Q000187:drug effects*; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006461:Hemolysis; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008751:Methylene Blue / Q000378:metabolism; D009129:Muscle Tonus / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism
D001095:Arachidonic Acids; D002121:Calcium Channel Blockers; D002118:Calcium; D008751:Methylene Blue