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# Influence of Extracellular pH on Intracellular pH and Cell Energy Status: Relationship to Hyperthermic Sensitivity

Mary Pat Fellenz and Leo E. Gerweck
Vol. 116, No. 2 (Nov., 1988), pp. 305-312
DOI: 10.2307/3577466
Stable URL: http://www.jstor.org/stable/3577466
Page Count: 8
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## Abstract

The effect of variable extracellular pH on intracellular pH, cell energy status, and thermal sensitivity was evaluated in CHO cells over the extracellular pH range of 6.0 to 8.6. Extracellular pH was adjusted with either lactic acid, HCl, or NaOH. Regardless of the method of pH adjustment, the results obtained were similar. The relationship between extracellular and intracellular pH was dependent upon the pH range examined. Intracellular pH was relatively resistant to a change in extracellular pH over the pH e range of 6.8 to 7.8 (i.e., $\Delta {\rm pH}_{{\rm i}}\simeq \Delta {\rm pH}_{{\rm e}}\times 0.33$). Above and below this range, $\Delta {\rm pH}_{{\rm i}}\simeq \Delta {\rm pH}_{{\rm e}}\times 1.08$ or × 0.76, respectively. Cellular survival after a 30-min heat treatment at 44°C remained constant over the extracellular pH range of 7.0 to 8.4, but varied substantially over a similar intracellular pH range. The cellular concentration of the high energy phosphate reservoir, phosphocreatine, decreased with decreasing pH. However, the cellular concentrations of ATP, ADP, and AMP remained constant over the entire pH range examined. It is concluded that increased thermal sensitivity resulting from a change in extracellular pH is not due to cellular energy depletion. Furthermore, intracellular pH is a more accurate indicator of thermal sensitivity than is extracellular pH.

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