Electrophysiological effects of vanilol on isolated papillary muscles of guinea pigs and atrioventricular conduction of rabbits

Vanilol (l-(2-methoxy-4-methoxycarbonyl-1-phenoxy)-3-isopropyl- amino-2-propanol), a derivative of protocatechuic acid with the same side chain as propranolol, could antagonize the experimental arrhythmias. Vanilol 1-100μmol/L caused a depression of Vmax of phase O in isolated papillary muscle cells of guinea pig. Vanilol (0.1, 1, 10μmol/L) prolonged the effective refractory period (ERP), and increased the rate of ERP/APD90, from 0.945±0.017 of control to 0.988±0.015 (P<0.05), 1.053±0.013 (P<0.01) and 1.043±0.011 (P<0,01). In the Tyrode’s solution of high K+, hypoxia and acidosis vanilol (10μmol/L) reduced the Vmax further. Vanilol, 5 and 10 mg/kg iv, prolonged P-R interval of ECG, A-H and H-V of HBE. Isoprenaline (Iso) only partially antagonized these prolongations but atropine did not. These results suggest that vanilol has characteristics of class 1 and 2 anti-arrhythmic agents.