Depression of jejunal dipeptide transport by pyridoxine deficiency in the rat.

Three dipeptides (L-alanyl-L-alanine, beta-alanyl-L-histidine and L-prolylglycine), representative of distinctly different transport groups, and a dicarboxylic acid dipeptide (L-glutamyl-L-glutamic acid) showed a quantitatively equivalent decrease of absorption (mean difference, 12% disappearance 15 min-1 5 cm-1) from jejunal loops in vivo in pyridoxine deficient rats, compared with pyridoxine-repleted controls. Analysis of results for seven dipeptides, including three studied previously, indicated that pyridoxine deficiency caused a general or non-specific reduction in dipeptide transport, similar for all dipeptides. Decrease in dipeptide transport in vitamin deficiency ran parallel to, but was significantly less than, the decrease in amino acid transport, suggesting in theory involvement of pyridoxine in a common cellular efflux mechanism or, less likely, in the energetics of active transport.