On the transport mechanisms of carnitine and its derivative in rat heart slices.

The transport of L-carnitine and analogs in exchange with previously loaded 3H-carnitine has been studied in heart tissue slices. The slices are first loaded with 3H-carnitine; then they are transferred in vessels containing the same medium with possible exchangers. Acetylcarnitine, L-carnitine, D-carnitine and deoxycarnitine exchange with internal 3H-carnitine. The exchange with acetylcarnitine, the largest among the compounds tested, appears to be a saturation process and is not affected either by oxidative phosphorylation and glycolysis inhibitors. The exchange of external acetylcarnitine with internal carnitine support that also in vivo heart tissue can utilize acetylcarnitine present in blood. Finally the observed deoxycarnitine/carnitine exchange, occurring in the reverse direction, may be the mechanism by which the heart accumulate external carnitine in exchange with endogenous deoxycarnitine.