Intracellular pH regulation in frog skin: a 31P-nuclear magnetic resonance study

The 31P-nuclear magnetic resonance spectra of single frog skins were monitored during perfusion with reference and experimental solutions, permitting each tissue to serve as its own series control. Over an external pH (pHo) range of approximately 7.25-7.64 U, the intracellular pH (pHc) displayed both homeostasis and response. External alkalinization produced a transient intracellular regulation, but pHc returned to its base-line value even in the absence of a further change in pHo. Below this range, pHc was linearly and strongly dependent on pHo with a slope close to 1, when the external pH was varied by addition of nonvolatile base. Measurements were generally performed with tissues bathed in Ringer solutions containing 2.5 mM HCO3- and bubbled with 99% O2-1% CO2. Replacement of external Cl- by gluconate reversibly increased pHc by 0.34 +/- 0.05 U. Substitution of SO4(2-) for Cl- also alkalinized the cells; pHc was increased by 0.16 +/- 0.01 U in the presence of the standard concentration of external HCO...