Effects of l-carnitine on membrane potential derangements induced by palmitoylcarnitine and anoxia in isolated superfused guinea-pig papillary muscle.

We examined in isolated superfused guinea-pig papillary muscle whether palmitoylcarnitine caused electrophysiological derangements similar to those caused by anoxia, and whether l-carnitine was similarly effective in improving membrane potential characteristics in both cases. Superfusion with Krebs-Henseleit solution containing 3 x 10(-4) M palmitoylcarnitine for 30 min caused gradual reduction of resting membrane potential and amplitude of action potential, and marked shortenings of the duration of action potential and absolute refractory period. On the other hand, aeration with 95%N2-5%CO2 for 30 min caused the same electrophysiological changes as those caused by palmitoylcarnitine. In both deteriorated preparations with palmitoylcarnitine superfusion and with 95%N2-5%CO2 aeration, l-carnitine (3 x 10(-3) M) prevented the papillary muscle from these derangements and restored the membrane potential at 10(-2) and 3 x 10(-2) M. It is concluded from these results that acylcarnitines such as palmitoylcarnitine, the accumulation of which has been thought to inhibit oxidative phosphorylation in ischemic heart, induce electrophysiological derangements quite similar to those found under anoxia, and that the application of l-carnitine is an effective solution to improve the electrophysiological derangements.