Milk carnitine affects organ carnitine concentration in newborn rats

Previous studies suggest that exogenous milk carnitine may be necessary during the suckling period to maintain normal fat metabolism. To characterize the relationship between milk carnitine and carnitine in body organs, newborn rats were fed from birth a rat milk substitute with or without 300 micromol/L L-carnitine, corresponding to the concentration present in rat milk, for either 2 or 4 d. Carnitine concentrations in heart, skeletal muscle, liver and small intestine were compared with levels in rat pups that were never fed (d 0) and those that were nursed by their mothers for 4 d. Carnitine supplementation resulted in significantly higher concentrations of carnitine in all organs studied after 4 d compared with nursed controls. Relative intestinal carnitine pool size was 38.1 +/- 3.0, 22.6 +/- 1.0, 7.9 +/- 0.5 and 2.3 +/- 0.7 micromol/g body wt in supplemented, nursed, unsupplemented and never fed pups, respectively (P < 0.05, compared with one another). These results indicate that carnitine organ concentrations are related to dietary intake during the early suckling period and that the small intestine is a considerable and previously unrecognized proportion of the carnitine pool of suckling animals.