Palmitoyl carnitine : an endogenous promoter of calcium efflux from rat heart mitochondria

The effects of the fatty acid ester palmitoyl carnitine (PC) on mitochondrial Ca2+ handling and ATP synthesis are described. At low concentrations (5–40 μM) PC was found to produce changes in mitochondrial Ca2+ handling, the most significant effect (P < 0.05) being the promotion of Ca2+ efflux (EC25 = 1.19 ± 0.11 μM). Studies on mitochondrial substrate oxidation in the presence of either glutamate plus malate, or succinate, confirmed the ability of PC (10–100 μM) to cause loss of respiratory control as shown by reductions in the Respiratory Control Index for each substrate. It was concluded that the effect of PC on Ca2+ transport was due to a direct action on the Na+---Ca2+ antiporter system, whilst the effect on respiration was due to an uncoupling action.