title: pH in principal cells of frog skin (Rana pipiens): dependence on extracellular Na+.
abstract: Measurements of intracellular pH (pHi) and of apical cell membrane potential (Va) were made in principal cells of frog skin (Rana pipiens) with double-barrel microelectrodes under open-circuit conditions. The tissues were pretreated with stilbenes (10(-3) M) and bathed in HCO3- -free NaCl Ringer solution that was buffered with 6 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (pH 7.8). Substitution of extracellular Na+ on both sides of the epithelium with N-methyl-D-glucamine caused intracellular acidification by 0.27 pH units. Restoration of Na+ on the apical side alone or on both sides caused a pHi recovery of 0.24 and 0.28 pH units, respectively, whereas return of Na+ on the basolateral side caused no recovery. Recovery of pHi on restoration of Na+ to the apical side was prevented by 10(-5) M 5-(N-ethyl-N-isopropyl)-amiloride. In individual preparations there was no correlation between pHi recovery due to return of apical Na+ and changes in Va. The average change in pHi was several times greater than the one expected from voltage clamp-induced changes in Va at constant extracellular Na+. The results suggest the presence of a Na+-H+ exchange on the apical side of principal cells. Such a process could be part of a negative feedback mechanism for regulation of Na+ entry via apical Na+ channels into principal cells.
authors.affiliation: Department of Physiology, Medical College of Virginia, Richmond 23298.
authors.forename: K
authors.initials: K
authors.lastname: Drewnowska
authors.forename: E J
authors.initials: EJ
authors.lastname: Cragoe
authors.forename: T U
authors.initials: TU
authors.lastname: Biber
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects; D011522:Protons; D011894:Rana pipiens; D012867:Skin / Q000187:drug effects; D012879:Skin Physiological Phenomena; D012964:Sodium / Q000494:pharmacology*
chemical_list: D011522:Protons; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000584:Amiloride; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C039614:ethylisopropylamiloride; D004121:Dimethyl Sulfoxide