EFFECTS OF ISCHEMIA AND POSTISCHEMIC REPERFUSION ON THE PASSIVE AND ACTIVE ELECTRICAL PARAMETERS OF RAT SKELETAL-MUSCLE FIBERS

Electrical parameters of extensor digitorum longus (EDL) muscles and t heir contralaterals were measured ''in vitro'' at 30 degrees C by a co mputerized two intracellular microelectrode technique after ischaemia and postischaemic reflow. In some muscles the adenosine triphosphate ( ATP) levels are also measured. Ischaemia led to a 39% reduction of Cl- conductance (G(Cl)), whereas reperfusion increase G(Cl) by 18% with r espect to contralateral control muscles. Ischaemia and reperfusion inc reased K+ conductance (G(K)) by 21% and 68%, respect ively; this incre ased was reversed by 50 mu M glybenclamide, suggesting an involvement of ATP-sensitive K+ channels. A statistically significant hyperpolariz ation and increase in excitability was observed after ischaemia, where as after the reflow period the fibres were depolarized and less excita ble. Ischaemia and reperfusion lowered the intracellular ATP content b y 18% and 64%, respectively.