Regulation of system y+ arginine transport capacity in differentiating human intestinal Caco-2 cells.
This study describes the ability of passaged human intestinal Caco-2 cells to regulate transport of L-arginine via system y+. Subconfluent and confluent cells possessed system y+ activity, as determined by the sodium independence of uptake and the pattern of inhibition by amino acid analogues or N-ethylmaleimide. Initial rates of arginine uptake via system y+ decreased as the cells advanced from the undifferentiated to the differentiated state following culture passaging. Furthermore, kinetic analysis of the leucine-insensitive portion of uptake indicated that the Caco-2 system y+ transport capacity decreased with cell age, dropping from a maximal velocity (Vmax) = 1,094 pmol.mg-1.min-1 [Michaelis constant (Km) = 41 microM] in undifferentiated cells 2 days postseeding to Vmax = 320 pmol.mg-1.min-1 (Km = 37 microM) in confluent cells 9 days postseeding (from cells of the same passage). Northern analysis indicated that the levels of a single 7.9-kb mCAT-1 mRNA species were relatively constant over the course of Caco-2 differentiation and therefore were unsynchronized with the system y+ relative transport activities. It is concluded that the Caco-2 capacity to transport arginine via system y+ may be downregulated by posttransitional modifications in confluent cells compared with newly passaged undifferentiated cells. These data serve as a well-defined in vitro model for further studies regarding regulation of arginine transport in epithelial cells.
Pan
M
M
Department of Physiology, College of Medicine, University of Florida, Gainesville 32610-0274, USA.
Malandro
M
M
Stevens
B R
BR
D000596:Amino Acids / Q000494:pharmacology; D001120:Arginine / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D005033:Ethylmaleimide / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology*; D007700:Kinetics; D007930:Leucine / Q000494:pharmacology; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism*; D011991:Receptors, Virus; D012964:Sodium / Q000494:pharmacology
D000596:Amino Acids; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011991:Receptors, Virus; C070506:ecotropic murine leukemia virus receptor; D001120:Arginine; D012964:Sodium; D007930:Leucine; D005033:Ethylmaleimide