Self-selection of dietary branched-chain amino acids by rats

The ability of rats to regulate branched-chain amino acid intakes was investigated by a self- sëlection feeding method. The relationship among the consumption of a branched-chain amino acid (BCAA), valine (Val), leucine (Leu), or isoleucine (lie) and the amino acid concentrations in plasma and brain were also studied. When weanling rats were offered a choice of two diets containing different level of Val, Leu, or lie, they consumed Val, Leu, or lie ranging from 0.53 to 2.07%, from 0.74 to 3.58%, and from 0.50 to 2.96% of the feed ingested, respectively. The amino acid concentrations in plasma and brain of the self-selecting rats were within a narrower range than those in the fixed feeding rats. From these results it became clear that when rats were allowed to select their feed, they could regulate Val, Leu, or lie intake to meet their requirement for the l-amino acid, and that these amino acid concentrations in plasma and brain were maintained within a narrow range.