O 2 occlusion and cyanide induced immediate relaxation and contraction of murine skeletal muscle

Abstract

The acute changes of muscle tone and membrane current upon occlusion of oxygenation (O 2 occlusion) were studied in vitro in mouse diaphragms. O 2 occlusion immediately produced a contraction and a relaxation, respectively, in ryanodine- and high K +-contracted muscles while a biphasic change (an initial decrease then a late increase) of muscle tone was produced in muscles contracted with caffeine. The O 2 occlusion effects were reversed after reoxygenation. CN − produced similar acute changes of muscle tone and abolished O 2 occlusion effects. The O 2 occlusion-induced relaxation in high K + medium was converted into a contraction by 3,4-diaminopyridine and by low Cl − Tyrode's. O 2 occlusion induced a small outward current and membrane hyperpolarization at a rate slower than the changes of muscle tone. Glybenclamide inhibited all of the changes induced by O 2 occlusion. It is possible that the K + and Cl − permeabilities of sarcoplasmic reticulum are highly sensitive to hypoxic challenge and related to the immediate changes of muscle tone after O 2 occlusion.