Glutamine transport in isolated epithelial intestinal cells. Identification of a Na+-dependent transport mechanism, highly specific for glutamine.
L-glutamine transport was evaluated in isolated cells from the guinea-pig small intestine by measuring [(3)H]- L-glutamine uptake. Villous and crypt cells expressed Na(+)-dependent and Na(+)-independent transport mechanisms. Glutamine transport systems were identified using various amino acids and analogues as inhibitors. In both villous and crypt cells, 2-(methylamino)-isobutyrate (MeAIB), a system A inhibitor, did not inhibit Na(+)-dependent glutamine influx. 2-Aminobicyclo(2,2,1)heptane-2-carboxylate (BCH), a system B(0) and B(0,+) substrate, had no effect on Na(+)-dependent influx. Serine, cysteine and threonine, system ASC inhibitors, reduced Na(+)-dependent influx by 50%. Asparagine, but not histidine, system N inhibitors, reduced Na(+)-dependent glutamine influx by 50%, however the effect of asparagine was not additive to that of threonine. The remaining Na(+)-dependent glutamine influx (50%) was only inhibited by glutamine itself, by Na(+) substitution ( N-methyl-glucamine, K(+), Li(+)) or by external pH reduction. Phenyl-acetyl-glutamine (PAG), a synthetic amino acid analogue, also inhibited this Na(+)-dependent, threonine-insensitive glutamine influx (IC(50) 2.45 mM). The Na(+)-independent uptake was partially inhibited by BCH, a system L inhibitor, and other neutral amino acids, but was not affect by PAG. Our results suggest that glutamine is transported in both villous and crypt cells by the Na(+)-independent system L, by the Na(+)-dependent system ASC and by an as yet undescribed Na(+)-dependent transport mechanism, highly specific for glutamine.
del Castillo
Jesús R
JR
Laboratorio de Fisiología Gastrointestinal, Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, PO Box 21827, Caracas 1020-A, Venezuela. jdelcas@ivic.ve
Súlbaran-Carrasco
María C
MC
Burguillos
Luis
L
D026905:Amino Acid Transport Systems / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002469:Cell Separation; D005973:Glutamine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics* / Q000494:pharmacology; D006168:Guinea Pigs; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D007477:Ions; D008297:Male; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D012964:Sodium / Q000378:metabolism*; D013912:Threonine / Q000494:pharmacology
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D007477:Ions; C037853:glutamine transport proteins; D005973:Glutamine; D013912:Threonine; C003089:phenylacetylglutamine; D012964:Sodium