Polarized amino acid transport by an epithelial cell line of renal origin (LLC-PK1). The basolateral systems.
The transport of three neutral amino acid analogs has been studied in an epithelial cell line from a pig kidney. 2-Aminoisobutyric acid is accumulated by LLC-PK1 cells against a concentration gradient through a mechanism with several features of a carrier-mediated process. The influx is accounted for by a saturable Na+-dependent and nonsaturable Na+-independent process. The total influx of 2-(methylamino)isobutyric acid is also mediated through Na+-dependent and Na+-independent systems. Part of the Na+-dependent influx of 2-aminoisobutyric acid was competitively inhibited by 2-(methylamino)isobutyric acid (Ki = 4.2 mM).l Selectivity studies indicate that the 2-(methylamino)isobutyric acid-sensitive part of 2-aminoisobutyric acid influx is mediated through the A system, whereas the insensitive part occurs through the ASC system. Cycloleucine transport also involves a Na+-dependent and Na+-independent process. The Na+-dependent influx is completely inhibited by 2-aminoisobutyric acid but not perceptibly by 2-(methylamino)isobutyric acid. This influx probably represents entry through the ASC system. The Na+-independent component is completely inhibited by 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid, a specific substrate for the L system. Uptake studies from either side of the monolayers indicate that these transport systems are exclusively located in basolateral membranes of the cultured renal cells.
D000596:Amino Acids / Q000378:metabolism* / Q000494:pharmacology; D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D004848:Epithelium / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011392:Proline / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D013552:Swine
D000596:Amino Acids; D000621:Aminoisobutyric Acids; D010042:Ouabain; D011392:Proline; D012964:Sodium; D011188:Potassium