L-Carnitine dissimilation in the gastrointestinal tract of the rat

Publisher Website
Google Scholar
Abstract
Previous studies in this laboratory and others have suggested that L-carnitine is degraded in the gastrointestinal tract of the rat, perhaps by the action of indigenous flora. L-[methyl-14C]Carnitine was administered to rats either orally or i.v. in doses of 86 nmol or 124 .mu.mol, and expired air, 48-h urine and fecal collections, and selected tissues at 48 h after isotope administration were examined for radiolabeled carnitine and metabolites. Urine and feces of rats receiving oral L-[methyl-14C]carnitine consistently contained 2 radiolabeled metabolites which were identified as trimethylamine N-oxide (primarily in urine) and .gamma.-butyrobetaine (primarily in feces). In these rats, these metabolites accounted for up to 23 and 31% of the administered dose, respectively. By contrast, for rats receiving i.v. L-[methyl-14C]carnitine or germ-free rats receiving the isotope orally or i.v., virtually all of the radioactivity recovered was in the form of carnitine. Analyses for 14CO2 and [14C]trimethylamine in expired air revealed little or no (< 0.1% of dose) conversion to these compounds, regardless of size or dose or route of administration. L-Carnitine is degraded in the gastrointestinal tract of the rat and indigenous flora are responsible for these transformations.