Quantitative contribution of NHE2 and NHE3 to rabbit ileal brush-border Na+/H+ exchange.
Quantitative contribution of NHE2 and NHE3 to rabbit ileal brush-border Na+/H+ exchange.
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NHE2 和 NHE3 对兔回肠刷状缘 Na /H 交换的定量贡献。
DOI：
10.1152/ajpcell.1998.274.5.c1261
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Donowitz,M
中科院分区：
文献类型：
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作者：
Wormmeester,L;SanchezdeMedina,F;Kokke,F;Tse,CM;Khurana,S;Bowser,J;Cohen,ME;Donowitz,M
肠道中性NaCl吸收由刷状缘（BB）Na+/H+交换与BB Cl−/交换组成，作为消化和消化道疾病的一部分上调和下调。糖皮质激素刺激回肠NaCl吸收和BB Na+/H+交换。肠BB含有两种Na+/H+交换亚型，NHE 2和NHE 3，但它们在兔回肠BB Na+/H+交换中的相对作用尚未确定。使用阿米洛利相关化合物HOE-694对分离NHE 2和NHE 3对回肠BB Na+/H+交换活性的贡献的技术进行标准化。在基础条件下，NHE 2和NHE 3均对回肠Na+/H+交换贡献约50%。糖皮质激素（甲基强的松龙）增加BB Na+/H+交换（2.5倍），但仅增加回肠NHE 3活性（4.1倍），对NHE 2活性无影响。因此，在用糖皮质激素处理的动物中，回肠BB Na+/H+交换为69%通过NHE 3。以NHE 3羧基端85个氨基酸与麦芽糖结合蛋白的融合蛋白为内标，建立了NHE 3的Western定量分析方法。糖皮质激素治疗增加了BB NHE 3的量。Western定量分析表明，NHE 3占对照兔回肠BB蛋白的0.018%，甲基强的松龙治疗兔回肠BB蛋白的0.042%（2.3倍）。甲基强的松龙治疗没有改变回肠BB NHE 2蛋白的量。在基础条件下，NHE 3周转数估计为458个周期/s，在糖皮质激素处理的回肠中为708个周期/s。因此，甲基强的松龙刺激回肠BB Na+/H+交换活动，只有对NHE 3的影响，而不是对NHE 2;它这样做主要是通过增加BB NHE 3的量，虽然它也增加了NHE 3的周转数。
Intestinal neutral NaCl absorption, which is made up of brush-border (BB) Na+/H+exchange linked to BB Cl−/exchange, is up- and downregulated as part of digestion and diarrheal diseases. Glucocorticoids stimulate ileal NaCl absorption and BB Na+/H+exchange. Intestinal BB contains two Na+/H+exchanger isoforms, NHE2 and NHE3, but their relative roles in rabbit ileal BB Na+/H+exchange has not been determined. A technique to separate the contribution of NHE2 and NHE3 to ileal BB Na+/H+exchange activity was standardized by using an amiloride-related compound, HOE-694. Under basal conditions, both NHE2 and NHE3 contribute ∼50% to ileal Na+/H+exchange. Glucocorticoids (methylprednisolone) increase BB Na+/H+exchange (2.5 times) but increase only ileal NHE3 activity (4.1 times), without an effect on NHE2 activity. Thus ileal BB Na+/H+exchange in animals treated with glucocorticoids is 69% via NHE3. A quantitative Western analysis for NHE3 was developed, using as an internal standard a fusion protein of the COOH-terminal 85 amino acids of NHE3 and maltose binding protein. Glucocorticoid treatment increased the amount of BB NHE3. The quantitative Western analysis showed that NHE3 makes up 0.018% of ileal BB protein in control rabbits and 0.042% (2.3 times as much) in methylprednisolone-treated rabbits. Methylprednisolone treatment did not alter the amount of ileal BB NHE2 protein. NHE3 turnover number was estimated to be 458 cycles/s under basal conditions and 708 cycles/s in glucocorticoid-treated ileum. Thus methylprednisolone stimulates ileal BB Na+/H+exchange activity only by an effect on NHE3 and not on NHE2; it does so primarily by increasing the amount of BB NHE3, although it also increases the NHE3 turnover number.