title: Changes of cytoplasmic pH in frog nerve fibers during K(+)-induced membrane depolarization.
abstract: Frog sciatic nerve and its thin bundles were loaded with fluorescein diacetate in order to monitor changes in cytoplasmic pH (pHi) caused by high K+ depolarization. Isosmotic substitution of external Na+ by K+ at pHo 7.3 led to a steady concentration-dependent (20-120 mM K+) decrease in pHi. Elevation of pHo from 7.3 to 8.5 prevented or even reversed these pHi changes, indicating their strong dependence on transmembrane H+ fluxes. The depolarization-induced intracellular acidification could not be prevented or decreased by any of the following treatments: removal of external Ca2+; application of the Ca2+ antagonists Ni2+ and Co2+; blockade of K+ channels by TEA; addition to the external solution of Zn2+, a blocker of putative voltage-sensitive H+ channels. By contrast, blockade of Na+ channels by 1-3 microM TTX prevented the effect of high K+ concentrations on pHi. It is concluded that the decrease in pHi induced by a prolonged membrane depolarization in frog nerve fibers is mainly due to an enhanced H+ influx through non-inactivating Na+ channels.
authors.affiliation: Ulyanovsk State Pedagogical University, Ulyanovsk, Russian Federation.
authors.forename: O N
authors.initials: ON
authors.lastname: Valkina
authors.forename: O V
authors.initials: OV
authors.lastname: Vergun
authors.forename: V B
authors.initials: VB
authors.lastname: Turovetsky
authors.forename: B I
authors.initials: BI
authors.lastname: Khodorov
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000502:physiology; D004558:Electric Stimulation; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D011895:Rana ridibunda; D012584:Sciatic Nerve / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013997:Time Factors
chemical_list: D026902:Potassium Channel Blockers; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D012964:Sodium; D011188:Potassium