L-GLUTAMINE AND L-ASPARAGINE STIMULATE NA+-H+ EXCHANGE IN PORCINE JEJUNAL ENTEROCYTES
L-GLUTAMINE AND L-ASPARAGINE STIMULATE NA+-H+ EXCHANGE IN PORCINE JEJUNAL ENTEROCYTES
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DOI：
10.1152/ajpgi.1994.266.5.g828
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发表时间：
1994-05-01
影响因子：
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通讯作者：
PARADISO, AM
中科院分区：
文献类型：
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作者：
RHOADS, JM;CHEN, W;PARADISO, AM
L-谷氨酰胺(Gin)是哺乳动物肠道细胞主要的呼吸燃料和核酸合成底物。结构上相关的氨基酸L-天冬酰胺(Asn)刺激结肠细胞中的增殖酶鸟氨酸脱羧酶，这一作用可被Na+-H+交换抑制剂阿米洛利阻断。在新生仔猪空肠上皮细胞系(IPEC-JB细胞)中，我们用计算机辅助显微荧光法测定了单个细胞内的pH(pH(I))，该细胞负载了对pH敏感的染料2‘，7’-bis(2-carboxyethyl)-5(6)-carboxyfluorescein.N-2-hydroxyethylpiperazine-N‘-2-ethanesulfonic酸缓冲液中的静息pH(I)为7.06+/-0.02。外源Na+的去除导致可逆酸化；pH(I)从NH4+诱导的酸负荷中恢复是Na+依赖的，阿米洛利是可抑制的，而不依赖于Cl-。Asn和Gin对静息pH(I)无明显影响，但Asn或Gin可使pH(I)从酸性刺激中持续增加一倍，这是L-脯氨酸、D-谷氨酰胺或L-苯丙氨酸所未见的。氨基氧乙酸酯对Gin代谢的抑制可阻断Gin对交换器的刺激作用。肿瘤促进剂佛波醇12-肉豆蔻酸酯13-醋酸酯(PMA)可促进酸负荷的恢复率，并增加静息pH(I)。PMA和Gin对酸负荷下Na+-H+交换的影响是相加的。蛋白激酶C抑制剂1-(5-isoquinolinylsulfonyl)-2-methylpiperazine.可抑制PMA而不是Gin对Na+-H+交换的刺激作用我们的结论是，Gin代谢通过一种不需要激活PKC的机制来刺激酸负荷的猪肠道细胞的Na+-H+交换。
L-Glutamine (Gin) 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-JB cells), we determined intracellular pH (pH(i)) by computer-assisted microfluorimetry in single cells loaded with pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Resting pH(i) 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 pH(i) from NH4+-induced acid load was Na+ dependent, amiloride inhibitable, and Cl- independent. Asn and Gin had no measurable effect on resting pH(i), but pretreatment with Asn or Gin induced a consistent twofold increase in pH(i) recovery from an acid challenge that was not seen with L-proline, D-glutamine, or L-phenylalanine. Inhibition of Gin metabolism by aminooxyacetate abolished the stimulatory effect of Gin on the exchanger. The tumor promotor phorbol 12-myristate 13-acetate (PMA) stimulated recovery rate from acid load and also increased resting pH(i). The effects of PMA and Gin on Na+-H+ exchange from acid load were additive. Stimulation of Na+-H+ exchange by PMA, but not by Gin, was inhibited by protein kinase C (PKC) inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine. We conclude that Gin metabolism stimulates Na+-H+ exchange of acid-loaded porcine enterocytes by a mechanism not requiring activation of PKC.