Uptake of L-[35S]cystine by isolated rat brain capillaries

Adult rat brain capillaries were isolated by a simplified procedure and showed an enrichment of the marker enzyme, gamma-glutamyltranspeptidase. The uptake of [35S]cystine at 37 degrees C by this preparation can be divided into two components, a sodium- and energy-dependent transport process for the free amino acid pool, with an apparent Km of 36 microM, and a binding process, with an apparent Km of 1.13 mM. Chemical analysis of the amino acid pool indicates that cystine is the major from of intracapillary 35S. Cystine transport was not inhibited by lysine, but glycine, alpha-methylaminoisobutyric acid and beta-2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid were inhibitory to a small extent.