Effect of structural analogues on intestinal accumulation of glycine

Abstract

Glycine uptake (1 x 10^–3 m) by hamster intestinal segments in vitro was studied after 20 min of incubation both in the absence and presence of various analogues (5 x 10^–3 m). A variety of chemical relatives of glycine with modifications of the —COOH, —NH₂, or α-hydrogen groups or with double modifications (such as ethanol) were without effect on glycine accumulation. Thus under these conditions glycine could not be displaced by its analogues. Three compounds, however, all α-amino acids, were effective in depressing glycine uptake (allylglycine, α-phenylglycine, l-alanine). Data are presented showing that two of these inhibitors are themselves transported and hence likely competed with the amino acid transport system. α-Aminoisobutyric acid and N-methylglycine, both known to be transported by the gut, did not interfere with glycine accumulation. In addition to oxalic acid, other succinic dehydrogenase inhibitors (hydrocinnamic acid, glutaric acid, malonic acid at 5 x 10^–3 m) were without major depressant effect on glycine accumulation by this system.