Characterization of chicken intestinal brush border membrane Ns/H exchange |
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Affiliation: | 1. Department of Medicine, Section of Gastroenterology, University of Chicago, Box 400, 5841 South Maryland Avenue, IL 60637, U.S.A. Tel.: (312) 702-6458; Fax: (312) 702-2182;3. P.O. Box 631548, Nachogdoches, TX 75963, U.S.A.;4. Department of Physiology and Biophysics, University of Illinois at Chicago, IL 60680, U.S.A. |
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Abstract: | - 1.1. Na/H exchange is the major pathway for Na uptake in brush border membrane vesicles from chicken small intestine. Hanes-Woolf analysis demonstrated that Na and H competed at the same extravesicular site. The KNa for Na+ at extravesicular pH 6.6 is 35 mM and at pH 7.4, 12 mM.
- 2.2. Similar to mammalian intestinal cells, the Na/H exchanger does not appear to have an internal proton modifier site. Varying intravesicular pH from 6.1 to 7.8 stimulates uptake, but a sigmoidal relationship is not observed.
- 3.3. The ability of several amiloride analogs to inhibit the exchanger was tested and the inhibitory profile was similar, but not identical to Na/H exchangers in mammalian tissues. The potency series (from most to least potent) is hexamethylamiloride ≈ ethylisopropylamiloride > methylisobutylamiloride > dimethyl-amiloride > amiloride.
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