Contractile and Electrical Characteristics of Extensor Muscle from Alloxan-Diabetic Rats: An In Vitro Study

Diabetes mellitus was produced by withholding insulin from female rats previously treated with alloxan. In vitro studies of contractile and electrical properties of the extensor digitorum longus muscle were analyzed at various periods following cessation of insulin treatment. In severely diabetic ketoacidotic rat muscles it was observed that both direct and indirectly induced twitch and tetanic tensions were significantly reduced to the same degree. Resting membrane potentials were significantly reduced but repolarized when external chloride was removed. Indirectly induced action potential amplitude and rate of depolarization were significantly depressed and there was a significant increase in action potential duration. Specific membrane in action potential duration. Specific membrane resistance decreased significantly but transiently due largely to an increase in chloride conductance and specific capacitance increased significantly. After extended periods of milder diabetes, specific tetanic tension decreased slightly while specific twitch tension was unchanged in both direct and indirectly induced contractions. Resting potentials were only slightly reduced. Indirectly elicited action potential amplitude and rate of depolarization were slightly reduced. Specific membrane resistance was significantly increased largely due to decreases in chloride conductance. Specific capacitance was unchanged.