Uptake of L-[14C]proline by isolated rat brain capillaries.
Rat brain capillaries exhibit concentrative uptake of L-proline. The uptake is mediated by two saturable systems, one with a Km of 0.11 mM and another with a Km of 5.9 mM. Entry also occurred by diffusion, especially at high substrate concentrations. The saturable high-affinity system is sodium-dependent, with a Km for sodium of 36 mM. Proline uptake is not inhibited by lysine, but is inhibited by phenylalanine, glycine, and leucine. alpha-Methylaminoisobutyric acid (MeAIB), a model for sodium-requiring transport systems, is a competitive inhibitor of the low-Km system. b-2-Aminobicyclo-[2,2,1]-heptane-2-carboxylic acid (BCH), a model for nonsodium-dependent transport, however, also inhibited proline uptake.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000098:blood supply*; D002196:Capillaries / Q000378:metabolism*; D002250:Carbon Radioisotopes; D007700:Kinetics; D008297:Male; D011392:Proline / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology
D002250:Carbon Radioisotopes; D011392:Proline; D012964:Sodium