title: L-glutamine and L-asparagine stimulate Na+ -H+ exchange in porcine jejunal enterocytes.
abstract: L-Glutamine (Gln) is a major respiratory fuel and substrate for nucleic acid synthesis in mammalian intestinal cells. The structurally related amino acid, L-asparagine (Asn), stimulates the proliferative enzyme ornithine decarboxylase in colonocytes, an effect that is blocked by the Na+-H+ exchange inhibitor amiloride. In an epithelial cell line derived from newborn piglet jejunum (IPEC-J2 cells), we determined intracellular pH (pHi) by computer-assisted microfluorimetry in single cells loaded with pH-sensitive dye 2',7'-bis(2-carboxyethyl)5-(6)- carboxyfluorescein. Resting pHi in N-2-hydroxyethylpiperazine-N'-2- ethanesulfonic acid-buffered NaCl Ringer was 7.06 +/- 0.02. Removal of external Na+ caused reversible acidification; recovery of pHi from NH+4-induced acid load was Na+ dependent, amiloride inhibitable, and Cl-independent. Asn and Gln had no measurable effect on resting pHi, but pretreatment with Asn or Gln induced a consistent twofold increase in pHi recovery from an acid challenge that was not seen with L-proline, D-glutamine, or L-phenylalanine. Inhibition of Gln metabolism by aminooxyacetate abolished the stimulatory effect of Gln on the exchanger. The tumor promotor phorbol 12-myristate 13-acetate (PMA) stimulated recovery rate from acid load and also increased resting pHi. The effects of PMA and Gln on Na+-H+ exchange from acid load were additive. Stimulation of Na+-H+ exchange by PMA, but not by Gln, was inhibited by protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpeperazine. We conclude that Gln metabolism stimulates Na+-H+ exchange of acid-loaded porcine enterocytes by a mechanism not requiring activation of PKC.
authors.affiliation: Department of Pediatrics, North Carolina State University School of Veterinary Medicine, Chapel Hill 27599.
authors.forename: J M
authors.initials: JM
authors.lastname: Rhoads
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: P
authors.initials: P
authors.lastname: Chu
authors.forename: H M
authors.initials: HM
authors.lastname: Berschneider
authors.forename: R A
authors.initials: RA
authors.lastname: Argenzio
authors.forename: A M
authors.initials: AM
authors.lastname: Paradiso
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000136:Acid-Base Equilibrium / Q000187:drug effects / Q000502:physiology; D000584:Amiloride / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001216:Asparagine / Q000494:pharmacology*; D002460:Cell Line; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005452:Fluoresceins; D005456:Fluorescent Dyes; D005973:Glutamine / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007546:Isoquinolines / Q000494:pharmacology; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008353:Mannitol / Q000494:pharmacology; D008536:Meglumine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; D007546:Isoquinolines; D010879:Piperazines; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D005973:Glutamine; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester; D008353:Mannitol; D008536:Meglumine; D001216:Asparagine; D000584:Amiloride; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D012964:Sodium; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate