TRANSPORT OF GLYCINE AND LYSINE ON THE CHLORIDE-DEPENDENT BETA-ALANINE (B-O,B--INTESTINE() CARRIER IN RABBIT SMALL)

Transport of glycine, lysine and beta-alanine in rabbit, guinea pig an d rat small intestine has been examined by measurements of the unidire ctional influx across the brush border membrane of the intact epitheli um. In rabbit distal ileum the chloride-dependent fraction of glycine transport, and all sodium- and chloride-dependent lysine transport is carried on the beta-alanine carrier. Lysine eliminates all saturable, sodium-independent transport of glycine. The saturable, sodium-depende nt, and lysine resistant influx of glycine is characterized by a K-1/2 (Gly) of 60 mM. Glycine transport in the mid intestine of the guinea p ig is chloride-independent and in the rat only a minute fraction may b e chloride-dependent. These species do not possess an equivalent of th e rabbit beta-alanine carrier. In conclusion, glycine transport in rab bit distal ileum is by the sodium-dependent carrier of neutral amino a cids, by the sodium-independent lysine carrier, and by the sodium- and chloride-dependent beta-alanine carrier which closely resembles the B -0,B-+ carrier described in mouse blastocysts. All sodium dependent ly sine transport in rabbit distal ileum is by the chloride- and sodium-d ependent beta-alanine carrier. It is proposed that the beta-alanine ca rrier in rabbit distal ileum be renamed the B-0,B-+ carrier.