EFFECTS OF PHTHALAZINOL, EG 626, ON MEMBRANE AND MECHANICAL PROPERTIES OF SMOOTH MUSCLE CELLS OF RABBIT MAIN PULMONARY ARTERY AND SUPERIOR MESENTERIC ARTERY

[摘要] References(28)Effects of phthalazinol, EG 626, on the membrane and mechanical properties of the vascular smooth muscles, namely superior mesenteric artery and main pulmonary artery of the rabbit were examined. EG 626 (10-7-3 × l0-5 g/ml) did not modify the membrane potential (-56.5 nmV), length constant of the tissue (1.47 mm), and rectifying property of the membrane in the pulmonary artery. The membrane potential of the mesenteric artery (-59.8 mV) was also not modified. By treatment with 10-5 g/ml EG 626, the mechanical responses of both muscle tissues induced by either direct muscle stimulation (1 sec pulse) or by nerve stimulation (0.5 msec, 30 Hz) were suppressed. The mechanical response induced by nerve stimulation was more dominantly suppressed than that induced by direct muscle stimulation. Dose-response curve obtained from the relation between noradrenaline and mechanical response in both pulmonary and mesenteric arteries shifted to the right by treatment with 10-5 g/ml EG 626. When the depolarization-contraction relationship was observed before and during application of EG 626 (10-5 g/ml), using the voltage clamp technique, the application of this agent raised the mechanical threshold to evoke contraction and amplitude of the contraction evoked at any given grade of depolarization was consistently reduced as compared with that evoked in Krebs Solution. These observations suggest that EG 626 suppresses the mobilization of Ca++ during contraction and also the release of chemical transmitter from the nerve terminals by suppression of Ca++ mobilization. EG 626 would thus appear to act on the vascular smooth muscles as a vasodilator.

[学科分类] 药理学