Regulation mechanisms of intracellular pH of Xenopus laevis oocyte

Biochim Biophys Acta. 1992 Oct 6;1137(1):45-51. doi: 10.1016/0167-4889(92)90098-v.


Intracellular pH values (pHi) of Xenopus oocytes were optically measured using a fluorescent dye, 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The oocytes were loaded with dye by incubation with a membrane-permeable form (BCECF-AM). Mean pHi of the oocytes in pH 7.6 solution was 7.69. Increasing ambient pCO2 rapidly decreased pHi and estimated buffering power was 23.8 mM/pH unit. Changing ambient HCO3- from 5 to 30 mM did not alter pHi. After incubation in a Na(+)-free solution, Na+ addition to the bath rapidly increased pHi and this response was blocked by amiloride (ED50 2 microM). The addition of NH4Cl to the bath caused an initial transient increase in PHi followed by a secondary decrease. The secondary decrease was greatly inhibited by a histidine specific reagent, diethylpyrocarbonate. It was also slightly inhibited by ouabain, Ba2+ and furosemide, but not by amiloride. These data suggest that (1), fluorescence technique is applicable to PHi measurements of Xenopus oocytes; (2), Xenopus oocytes have an amiloride sensitive Na+/H(+)-exchange, and permeabilities to CO2, NH3, and NH+4. These observation may be useful in studying the relationship between pHi and oocytes development, and the expression of acid/base transporters in Xenopus oocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ammonia / metabolism
  • Animals
  • Bicarbonates / metabolism
  • Carbon Dioxide / metabolism
  • Cell Membrane Permeability
  • Fluoresceins
  • Hydrogen / metabolism
  • Hydrogen-Ion Concentration
  • Oocytes / physiology*
  • Sodium / metabolism
  • Spectrometry, Fluorescence
  • Xenopus laevis


  • Bicarbonates
  • Fluoresceins
  • Carbon Dioxide
  • Ammonia
  • Hydrogen
  • 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein
  • Sodium