Na-H exchange in rat liver basolateral but not canalicular plasma membrane vesicles.

摘要: Na+-stimulated H+ movement and H+-stimulated Na+ uptake were studied in basolateral (blLPM) canalicular (cLPM) rat liver membrane vesicles. was monitored with the fluorescent amine acridine orange; 22Na assayed by a rapid Millipore filtration technique. In blLPM, inwardly directed gradients stimulated efflux outwardly proton influx. Outwardly (pH 5.9/pH out 7.9) initial rates 5- to 10-fold over pH-equilibrated conditions 7.9/pH 7.9). Conversely, 5.9) inhibited uptake. pH-dependent amiloride harmaline but not other transport inhibitors, bumetanide, furosemide, 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, acetazolamide. Lithium also Although component of pH-stimulated appeared be dependent on potential, this electrogenic insensitive. Proton gradient-stimulated blLPM saturable, Km 5.4 mM Vmax 14 nmol . min-1 mg prot-1. contrast, cLPM, no occurred. These findings establish an electroneutral Na-H antiport cLPM liver. The polarity exchanger supports model bile formation that is dependent, part, HCO-3 and/or OH- excretion.