Changes in intracellular K+ concentration and action potential of myocardiocytes in early stage of radiation, burn and combined radiation-burn injuries in rats

K+-ISME and micro electrode were used respectively to measure the [K+]i concentration and action potential in ventricular papillary myocardiocytes of 92 Wistar rats, which were divided into four groups: normal rats (group C), and rats receiving radiation (group R), burn (group B) and combined radiation-burn (group RB), and undergoing measurement 1,3,8 and 24 hours after respective treatment. It was found that (1) [K+]i was reduced in groups B and RB (especially in group B), but there was no change in group R; (2) RP, APA and Vmax were all decreased in three injured groups; (3) APD50 and APD90 were shortened obviously in group B, but were prolonged in both groups R and RB (especially in group R). These results suggest that (1) radiation injury diminishes Na+ inflow and K+ outflow; (2) burn diminishes Na+ inflow and accelerates K+ outflow; (3) combined radiation-burn injury is not a simple addition of radiation and burn effects