Effects of L-propionylcarnitine on Electrical and Mechanical Alterations Induced by Amphiphilic Lipids in Isolated Guinea Pig Ventricular Muscle

We examined the effects of L-propionylcarnitine (Prop. C), a short-chain acylcarnitine, on amphiphile (L-lysophosphatidylcholine or L-palmitoylcarnitine)-induced electrophysiological and ultrastructural changes in isolated guinea pig ventricular papillary muscles, under acidic conditions (pH 6.9). Conventional microelectrode, tension-recording, and electron microscope techniques were used. Both amphiphiles, at a concentration of 10(-4) M, significantly decreased the resting membrane potential, action potential amplitude, and action potential duration, but increased the developed and resting tension. Such amphiphile-induced electrical changes were not observed in muscles pretreated with the beta-blocker, atenolol, although the mechanical changes remained unaffected. The application of Prop. C (10(-2) M), in the continued presence of the amphiphiles caused a return of the action potential duration and the developed tension to the control level. However, the resting potential and action potential amplitude remained unaffected; in fact, the maximum upstroke velocity (Vmax) of the action potential tended to decrease further. Pretreatment with Prop. C prevented all the amphiphile-induced electrophysiological and mechanical changes, except for Vmax. Electron microscopic studies revealed that amphiphile-induced ultrastructural changes were prevented, at least in part, in the presence of Prop. C. Thus, Prop. C antagonizes some of deleterious effects of amphiphiles, such as lysophosphatidylcholine and palmitoylcarnitine, upon the electrical and mechanical activities of the ventricular muscle, under acidic conditions.