Chemical form of dietary l-Carnitine affects plasma but not tissue Carnitine concentrations in male Sprague-Dawley rats

In Experiment 1, rats (n = 54) were randomly assigned to control or one of the four sources of l-Carnitine supplemented at either 100 or 200 μmol/kg/day and were allowed to acclimate for 14 days. Following a 12-h fast, plasma samples were obtained at 0, 5, 10, 15, 30, 60, 120, 240, 480 and 720 min after l-Carnitine feeding and assayed for free l-Carnitine concentration. Plasma-free l-Carnitine levels were affected by time after treatment intake (p < 0.0001) and l-Carnitine source (p < 0.0001). The time x source interaction was not statistically significant (p = 0.99). In Experiment 2, rats (n = 54) were randomly assigned to control or one of the four sources of l-Carnitine at either 100 or 200 μmol/kg/day and were acclimated as in experiment 1. Rats were sacrificed 120 min after feeding. Samples of liver and skeletal muscle were obtained and assayed for free l-Carnitine concentration. Neither skeletal muscle (p = 0.44) or liver (p = 0.59) tissue concentrations of l-Carnitine were affected by any l-Carnitine source as compared with the control. We conclude that some differences exist in plasma concentrations of free l-Carnitine following ingestion of different chemical forms of l-Carnitine. It is unclear if these differences in the circulating concentration of free l-Carnitine translate into any physiological differences for the animal. In this study, chemical form of l-Carnitine had no effect on skeletal muscle or liver tissue concentrations of l-Carnitine in young male Wistar rats.