Impairment of glycine absorption by glucose and galactose in man

Abstract

SUMMARY1. In order to investigate a possible competition for intestinal transport between amino acids and monosaccharides in man, iso-osmotic solutions containing (A) 100 m-mole glycine 1.-i, (B) 100 m-mole glycine and 200 mmole monosaccharide (glucose or galactose) 1.-i, and (C) 200 m-mole monosaccharide 1.-i, were successively perfused into the upper jejunum of twelve African Zambian patients. None had clinical evidence of malnutrition or small-intestinal disease. By using a double-lumen tube and by reference to a non-absorbable marker (polyethylene glycol, 4000), the rates of absorption of these substances have been calculated for a 30 cm jejunal segment.2. The presence of glucose and galactose produced a significant impairment (up to 50 %) in the rate of absorption of glycine. There was also a significant decrease in the uptake of both monosaccharides from the solutions in which glycine was also present. 3. If this observation also applies to other amino acids it could have a practical value in population groups living on high carbohydrate diets with a marginal concentration of some essential amino acids. It could have special importance when the jejunal mucosa is damaged in severe malnutrition or gastrointestinal infection. This impairment of amino acid uptake may explain the very high incidence of genetically determined lactasedeficiency in Africa.

Effect of glycylglycine and glycine on jejunal absorption rate of L‐histidine in man in vivo

“…The mean absorption rate of L-histidine (from a 100 m-mole 1.-i solution) has been compared with mean rates for glycine and L-methionine (also from 100 m-mole 1.-i solutions) in similar groups of Zambian African subjects who were studied by the same technique (Cook, 1971(Cook, , 1972c. The mean absorption rates for L-histidine, glycine and methionine are 43-5 (32-54) (n = 6) (present study), 42-1 (30-48) (n = 12) (Cook, 1971), HISTIDINE GL YCINE GL YC YLGL YCINE ABSORPTION 193 and 31*7 (21-39) (n = 8) (Cook, 1972c) m-mole (30 cm jejunum)-l hr-' respectively.…”

“…= 5; paired t test). Mean glycine absorption rate from solution D is significantly lower than that in twelve similar Zambian African subjects previously studied (Cook, 1971) (t = 4-050; d.f. = 16; P < 0-001; unpaired t test).…”

“…H .0 EQ glycylglycine in the various solutions were calculated as described by Cook (1971). Net water transfer rate was determined as described by Cook (1971). Table 2 summarizes the reproducibility of the results for the three 10-min collections during each perfusion (Cook, 1972b).…”

“…The technique of jejunal perfusion has been described by Cook (1971). Table 1 shows the position of the proximal opening of the double-lumen tube at the beginning of the investigation.…”

“…H .0 EQ glycylglycine in the various solutions were calculated as described by Cook (1971). Net water transfer rate was determined as described by Cook (1971).…”