Multiple effects of salicylaldoxime on rat cardiac action potentials

The effect of salicylaldoxime, 2-(OH)C6H4CH = NOH, on the resting membrane potential and action potential characteristics was studied using isolated right ventricular strips from rat heart. Salicylaldoxime (1-3 mM) reversibly hyperpolarized the cells, increased action potential amplitude, decreased the maximal rate of rise (Vmax) and prolonged duration. The prolongation of the action potential produced by 1 mM salicyaldoxime could not be reversed with isoprenaline (10 microM). Salicyalaldoxime (0.3-1 mM) had no effect on the Ca(2+)-dependent slow action potential for periods up to 60 min. Initial exposure to 3 mM salicylaldoxime 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 salicyaladoxime can block Na+, K+ and Ca2+ currents in rat cardiac muscle. Furthermore, it appears that the slow inward Ca2+ current, as measured by the slow action potential, may be sensitive to a dephoshorylating action of this oxime.