Glycyl-L-leucine transport in the rat small intestine

Publisher Website
Google Scholar
Abstract
The uptake of the peptide glycyl-L-leucine across the brush border of the rat small intestinal enterocyte was studied using everted rings. The transfer of leucine from the dipeptide into the enterocyte was greater than the glycine uptake from glycyl-L-leucine. This additional component for leucine transport was abolished by the removal of Na, by the presence of 10 mM L-alanine .beta.-naphthylamide and by excess free leucine. In contrast, the uptake of glycine from glycyl-L-leucine was not Na-dependent and was not reduced by the presence of excess free leucine. The presence of harmaline over a concentration range up to 10 mM inhibited some of the peptide-bound leucine and glycine uptake. Transport of leucine from glycyl-L-leucine in the presence of 20 mM free leucine was competitively inhibited by glycyl-L-proline, although not completely. In the rat, the Na-sensitive component of amino acid uptake from the dipeptide represents free amino acid liberated by superficial hydrolysis, while the transport of the intact peptide is not Na dependent. In addition, there are at least 2 routes of entry for the intact dipeptide glycyl-L-leucine, only one of which is shared with glycyl-L-proline.