Effects of metallothionein on action potentials of anoxic and reoxygenated papillary muscles of guin

AIM: To study anti-arrhythmic effects of metallothionein (MT). METHODS: Standard microelectrode technique was used to study the effects of MT on action potentials (AP) in anoxic and reoxygenated papillary muscles of guinea pigs. RESULTS: MT (002 mmol·L-1) had no effects on AP of the normal papillary muscles; when the muscles were exposed to ischemic solution without MT, there was a marked shortening of action potential duration (APD) at 20 %, 50 %, and 90 % of repolarization (APD20, APD50, APD90) from 82±7 to 37±7, 131±35 to 63±11, and 167±12 to 100±19 ms, respectively, (P<001); and an obvious reduction of resting potential (RP), action potential amplitude (APA), and the maximal upstroke velocity of phase 0 ( V max ) from -92±9 to -63±12 mV, 135±13 to 80±8 mV, and 286±55 to 164±42 V·s-1, respectively (P<001). However, in the presence of MT, the AP parameters (RP, APA, and Vmax) changed from -63±2 to -82±1 mV, 80±8 to 104±25 mV, and 164±42 to 237±43 V·s-1, respectively, (P<001), except that APD20, APD50, and APD90 shortened further from 37±7 to 12±3, 63±11 to 28±7, and 100±19 to 82±11 mV, respectively (P<001). MT decreased the incidence of automaticity during reoxygenation from 91 % to 33 % . CONCLUSION: MT possesses a calcium regu￣la￣tory property.