Impaired carnitine transport in the rat heart during E. coli sepsis

To determine the mechanism for the reduced content of myocardial carnitine during gram-negative sepsis, carnitine transport was examined in isolated perfused hearts. Rats were injected i.v. with 8 x 10(7) live colonies of E. coli per 100 g body weight or physiological saline. All rats were fasted after injection for 22 hr to equalize the differences in food intake. Total carnitine uptake in the hearts from both groups was essentially linear between 10 and 20 min of perfusion with 40 microM of carnitine. However, total uptake was significantly reduced by approximately 30% in the hearts from the E. coli-treated rats. In addition to the significant reduction in total carnitine uptake at 40 microM, uptake was significantly lower at 100 microM perfusate carnitine in hearts from E. coli-treated rats. However, total uptake was not significantly different between the groups at 200 and 300 microM perfusate carnitine. Carnitine uptake in the presence of 0.05 M mersalyl acid was comparable in both groups of hearts at all perfusate carnitine concentrations indicating no change in the diffusion component of transport in the hearts from the fasted E. coli-treated rats. The reduction in total uptake at 40 microM and 100 microM of perfusate carnitine was due to a 42% and 26%, respectively, decrease in the carrier-mediated uptake. This data suggests that the reduced content of myocardial carnitine in fasted E. coli-treated rats is due to the decrease in the carrier-mediated component of transport.