Effect of starvation on neutral amino acid transport in isolated small-intestinal cells from guinea pigs.
The effects of starvation on neutral amino acid transport were examined in isolated enterocytes. Starvation stimulated L-alanine transport by the Na(+)-dependent system A and the Na(+)-independent system L without producing any changes in either the Na(+)-dependent systems ASC or the passive non-mediated uptake. Starvation produces a twofold increase in Vmax of system A without any change in Kt. Starvation produces an increase in Vmax of system L of 1.7 times without any change in Kt. Activation of systems A and L by starvation was reversible with subsequent refeeding. The effects of a series of amino acids on systems A and L were evaluated. A different inhibition pattern was found in starved animals as compared to controls. Starvation increases Na(+)-dependent L-alanine uptake and Na(+)-independent cycloleucine uptake by small-intestinal brush-border membrane vesicles. These results suggest that starvation stimulates amino acid transport across the apical plasma membrane of the enterocytes by inducing specific carrier units.
Muñíz
R
R
Laboratorio de Fisiología Gastrointestinal, Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas.
Burguillo
L
L
del Castillo
J R
JR
D000409:Alanine / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D003515:Cycloleucine / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects*; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism; D008297:Male; D012964:Sodium / Q000494:pharmacology; D013217:Starvation / Q000378:metabolism*; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D000596:Amino Acids; D003515:Cycloleucine; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D012964:Sodium; D000409:Alanine