EFFECTS OF LONG-CHAIN AND MEDIUM-CHAIN TRIGLYCERIDES ON AMINO-ACID-UPTAKE IN RAT INTESTINAL BRUSH-BORDER MEMBRANE-VESICLES

1. Uptake of L-leucine, L-phenylalanine, L-proline and L-lysine into b rush border membrane vesicles from rats fed either a medium-chain trig lyceride (MCT) or a long-chain triglyceride (LCT) diet was studied und er conditions of the presence or absence of a Na+ gradient. 2. From th e results of initial rate, Na+-dependent transport in LCT feeding were lower than in feeding MCT. The Na+-independent transport did not vary in either group except for L-lysine uptake. 3. For L-leucine, L-pheny lalanine and L-proline in Na+ dependence, kinetic analysis revealed 4- 6-foId smaller V-max values in LCT group than in MCT group. L-Lysine i n Na+-independent transport was 10-fold lower in LCT group than in MCT group. The K-m values were not affected by feeding the LCT or MCT die t. 4. It is clear that amino acid transport is regulated by different types of dietary fat. We consider that the alteration of transport act ivity is attributable to the changes in number of membrane-bound trans port carriers but not to their affinity.