Utilization of Methionine by the Adult Rat: II. Absorption and Tissue Uptake of L- and DL-Methionine

Abstract

The absorption of l- and dl-methionine-C14H3 from the alimentary tract and the distribution of radiocarbon from these sources and dl-methionine-2-C14 in blood components and 18 tissues of rats were investigated. Small, but statistically significant differences in the absorption and tissue uptake of l- and dl-methionine were observed in these experiments. The absorption of l-methionine is calculated to be 1.1 times that of its d- isomer.After 30 minutes, the plasma and plasma proteins of rats fed l-methionine-methyl-C14 contained greater activity than the corresponding components of rats fed the dl-form of this compound. More radiocarbon was observed in plasma, protein-free plasma, and plasma protein of rats fed dl-methionine-2-C14 than in those components of rats fed the methyl-labeled dl-compound.The variation in tissue response of individual animals similarly treated to uniform doses of l- and dl-methionine-methyl-C14 and dl-methionine-2-C14 has been measured. During a 30-minute interval, the greatest amount of variability in uptake of l-methionine occurred in pancreas, liver, bone marrow and thyroid.Significantly greater concentrations of radiocarbon were present in brain, lungs, liver, and heart of rats fed l-methionine-methyl-C14 than in those tissues of rats fed the dl- form of this amino acid. The concentration of the methyl carbon of methionine in liver was significantly greater than that of the alpha-carbon.