title: Role of monocarboxylic acid transport in intracellular pH regulation of isolated proximal cells.
abstract: Isolated proximal cells were prepared from rabbit kidney cortex by mechanical dissociation. The intracytoplasmic pH (pHi) was measured in HCO3(-)-free media (external pH (pHe), 7.3) using the fluorescent dye 2,7-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). Cells were acid-loaded by the nigericin technique. Addition of 70 mM Na+ to the cells caused a rapid pHi recovery, which was blocked by 0.5 mM amiloride. When the cells were exposed to 5 mM sodium butyrate in the presence of 1 mM amiloride, the H+ efflux was significantly increased and followed Michaelis-Menten kinetics. Increasing pHe from 6.4 to 7.6 at a constant pHi of 6.4 enhanced the butyrate activation of the H+ efflux. Increasing pHi from 6.5 to 7.2 at a constant pHe of 7.2 reduced the butyrate effect. 22Na uptake experiments in the presence of 1 mM amiloride showed that 1.5 mM butyrate increased the Na+ flux in the proximal cells (pHi 7.10). The efficiency of monocarboxylic anions in promoting a pHi recovery increased with the length of their straight chain (acetate less than propionate less than butyrate less than valerate). The data show that when the Na+/H+ antiporter is blocked, the proximal cells can regulate their pHi by a Na+-coupled absorption of butyrate followed by non-ionic diffusion of butyric acid out of the cell and probably also by OH- influx by means of the OH-/anion exchanger.
authors.affiliation: Department of Biologie, CEN Saclay, Gif-sur-Yvette, France.
authors.forename: M
authors.initials: M
authors.lastname: Bidet
authors.forename: J
authors.initials: J
authors.lastname: Merot
authors.forename: M
authors.initials: M
authors.lastname: Tauc
authors.forename: P
authors.initials: P
authors.lastname: Poujeol
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002264:Carboxylic Acids / Q000378:metabolism*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D011190:Potassium Cyanide / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
chemical_list: D002087:Butyrates; D002264:Carboxylic Acids; D020148:Butyric Acid; D000584:Amiloride; D012964:Sodium; D011190:Potassium Cyanide