ALTERATION OF THE VOLTAGE-DEPENDENCE OF THE TWITCH TENSION IN FROG SKELETAL-MUSCLE FIBERS BY A POLYETHER, BISTRAMIDE-A

Bistramide A, a toxin isolated from Lissoclinum bistratum Sluiter, was applied to frog skeletal muscle fibres. Micromolar concentrations of toxin decreased the amplitude of the twitch tension. Bistramide A shif ted the activation and the steady-state inactivation characteristics o f the tension on the voltage axis towards more positive and negative m embrane potentials respectively. The data suggest that Bistramide A bi nds to the activated and inactivated state of the dihydropyridine-rece ptor which senses the T-tubule membrane potential.