Effects of ischaemia and post-ischaemic reperfusion on the passive and active electrical parameters of rat skeletal muscle fibres.

Electrical parameters of extensor digitorum longus (EDL) muscles and their contralaterals were measured "in vitro" at 30 degrees C by a computerized two intracellular microelectrode technique after ischaemia and post-ischaemic reflow. In some muscles the adenosine triphosphate (ATP) levels are also measured. Ischaemia led to a 39% reduction of Cl- conductance (GCl), whereas reperfusion increase GCl by 18% with respect to contralateral control muscles. Ischaemia and reperfusion increased K+ conductance (GK) by 21% and 68%, respectively; this increased was reversed by 50 microM glybenclamide, suggesting an involvement of ATP-sensitive K+ channels. A statistically significant hyperpolarization and increase in excitability was observed after ischaemia, whereas after the reflow period the fibres were depolarized and less excitable. Ischaemia and reperfusion lowered the intracellular ATP content by 18% and 64%, respectively.