Abstract
Summary
The intestinal transport of l-Phe from 1 and 2 mM solutions in the presence of variable concentrations of l-Ala was studied with an in vivo technique utilizing 20-cm long jejunal segments in anesthetized rats. The simultaneous perfusion of l-Ala inhibited the absorption of l-Phe when the molar ratio l-Ala:l-Phe was 10:1 or higher. The results suggested a noncompetitive type of inhibition under the experimental conditions described. Other essential amino acids such as l-lysine, l-histidine, and l-methionine at 2 mM concentrations were also significantly inhibited by 40 mM l-Ala. These data are consistent with the presence of two active transport mechanisms for neutral amino acids in the intestinal mucosa: a common one which can be blocked by large concentrations of l-Ala, and a specific site or carrier which is not affected by this inhibitor.
We thank the technical assistance of Susan A. Moak.
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