The rabbit jejunal 'imino carrier' and the ileal 'imino acid carrier' describe the same epithelial function

For rabbit jejunal brush border vesicles an 'imino carrier' has been defined as a sodium-depedent, alanine-resistant transporter of cyclic imino acids, while for intact rabbit jejunal and ileal epithelia an 'imino acid carrier' has been defined as a sodium-dependent transporter of both aliphatic and cyclic imino acids. This study on intact rabbit intestine examines whether these two terms describe the same epithelial function. The K _{1 2}^Pro and the K_i^Pro against J_mc ^MeAIB are identical and so are K _{1 2}^MeAIB and K_i^MeAIB against J_mc^Pro. Likewise, K_i^Leu is tha same against the transport of both proline and MeAIB. Is is, therefore, concluded that the terms 'imino carrier' and 'imino acid carrier' describe the same epithelial function: A sodium-dependent, relatively high afinity, saturable transporter of both aliphatic and cyclic imino acids. Estimates of the apparent affinity and inhibitory constants for MeAIB, proline and leucine confirm that the jejuno-ileal variation of amino acid transport along the rabbit small intestine is a variation of maximal transport capacity.