Does lindane (gamma-hexachlorocyclohexane) increase the rapid delayed rectifier outward K(+) current (I(Kr)) in frog atrial myocytes?

BACKGROUND: The effects of lindane, a gamma-isomer of hexachlorocyclohexane, were studied on transmembrane potentials and currents of frog atrial heart muscle using intracellular microelectrodes and the whole cell voltage-clamp technique. RESULTS: Lindane (0.34 microM to 6.8 microM) dose-dependently shortened the action potential duration (APD). Under voltage-clamp conditions, lindane (1.7 microM) increased the amplitude of the outward current (I(out)) which developed in Ringer solution containing TTX (0.6 microM), Cd(2+) (1 mM) and TEA (10 mM). The lindane-increased I(out) was not sensitive to Sr(2+) (5 mM). It was blocked by subsequent addition of quinidine (0.5 mM) or E-4031 (1 microM). E-4031 lengthened the APD; it prevented or blocked the lindane-induced APD shortening. CONCLUSIONS: In conclusion, our data revealed that lindane increased the quinidine and E-4031-sensitive rapid delayed outward K(+) current which contributed to the AP repolarization in frog atrial muscle.