MULTIPLE EFFECTS OF SALICYLALDOXIME ON RAT CARDIAC ACTION-POTENTIALS

The effect of salicylaldoxime, 2-(OH)C6H4CH=NOH. on the resting membra ne potential and action potential characteristics was studied using is olated right ventricular strips from rat heart. Salicylaldoxime (1-3 m M) reversibly hyperpolarized the cells, increased action potential amp litude, decreased the maximal rate of rise (V-max) and prolonged durat ion. The prolongation of the action potential produced by 1 mM salicya ldoxime could not be reversed with isoprenaline (10 mu M). Salicyalald oxime (0.3-1 mM) had no effect on the Ca2+-dependent slow action poten tial for periods up to 60 min. Initial exposure to 3 mM salicylaldoxim e produced no changes in the slow action potential. but after 30 min. there was a gradual reduction in amplitude. This effect was completely reversible within 10-15 min. of washout. These data suggest that sali cyaladoxime can block Na+, K+ and Ca2+ currents in rat cardiac muscle. Furthermore, it appears that the slow inward Ca2+ current, as measure d by the slow action potential, may be sensitive to a dephosphorylatin g action of this oxime.