Enhancement of ouabain arrhythmias by fatty acids.
Possible enhancement by free fatty acids (FFA) of the arrhythmogenic actions of ouabain was studied in rabbits. The mean dose of ouabain required for inducing ventricular tachycardia or fibrillation in conscious animals was significantly lowered by intravenous injection of 5 ml of a 20% fat emulsion (Lipofundin), which significantly elevated circulating FFA. Lipofundin alone did not initiate arrhythmias in another group of animals. The transmembrane action potential duration (APD) and the maximum rate of depolarization (Vmax)recorded from rabbit papillary muscles were markedly reduced under the influence of 2 mM octanoate, a short-chain FFA. Ouabain, 10(-7M), reduced significantly only the APD measured at zero level of repolarization. In papillary muscles exposed to both octanoate and ouabain, resting potential, overshoot, APD, and Vmax were all significantly decreased below control values. The synergistic arrhythmogenic actions of FFA and ouabain might be explained by the inhibiting effect of both agents on membrane (Na+ + K+)ATPase.
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D004357:Drug Synergism; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D011817:Rabbits; D013610:Tachycardia / Q000139:chemically induced; D014693:Ventricular Fibrillation / Q000139:chemically induced
D005230:Fatty Acids, Nonesterified; D010042:Ouabain