The transport of glutamine and alanine into rat colonocytes

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Abstract
1. The transport of glutamine and alanine into isolated rat colonocytes was studied. 2. The transport of both amino acids appears to be dependent on a Na+ gradient. 3. The apparent Km values for the transport of glutamine and alanine were 2.56 .+-. 0.84 and 5.35 .+-. 1.20 mM respectively, but with similar Vmax, values. 4. Glutamine and alanine transport were mutually competitive, and the transport of both amino acids was competitively inhibited by 2-methylaminoisobutyrate. In contrast, histidine inhibited the transport of both glutamine and alanine non-competitively. 5. It is concluded that glutamine and alanine are transported into rat colonocytes by a common carrier system similar to System A of other cells. 6. It is suggested that the metabolic function of this transport system in rat colonocytes might be the partial exchange of extracellular glutamine for intracellular alanine.