Amino acid transport by the small intestine of the rat. Effects of glucose on transintestinal transport of proline and valine

Abstract

The effects of galactose and glucose on transport of proline and valine by the rat small intestine have been studied using an everted sac preparation. 1. 1. Two magnitudes of sacs were used; small sacs 7–8 cm long and large sacs 17 cm. long. 2. 2. Galactose inhibited the transport of both amino acids. 3. 3. Glucose eliminated completely the inhibitory effect of galactose. 4. 4. Glucose did not influence the degree of tissue accumulation or the serosal concentrations of proline or valine found at the end of a 60-min incubation. 5. 5. Glucose increased markedly the net flux of water to the serosal fluid. 6. 6. In the small sacs with relatively small increments of the serosal fluids the transport of amino acid was not significantly enhanced in the presence of glucose. But in the large sacs with a prodigious increase in serosal volume a highly significant enhancement was found. 7. 7. The glucose effect on amino acid transport by the large sacs was closely simulated, when the glucose effect on the serosal fluid volume was simulated by different means. This, however, was not the case if the amino acid transport was subject to inhibition by galactose. 8. 8. It is concluded that glucose enhances the transport of amino acids by the rat small intestine by: 1. (a) providing an energy supplement which allows the amino acid carrier to perform and maintain the control degree of epithelial accumulation in spite of a simultaneous expenditure of energy on sugar accumulation and by: 2. (b) increasing the net transintestinal water flux, and so increasing the compartment with which the accumulating epithelium equilibrates.