VARIATION OF INTRACELLULAR INHIBITION WITH pH 



717 



These two simple and extreme cases introduce us to the proljlems that 

 must be encountered when one attempts to formulate the pH dependence 

 of intracellular inhibition. These basic problems revolve around the un- 

 certainty and variability in the intracellular pH. the nature and the effi- 

 ciency of the buffers within the cell, and the permeability properties of 

 the cell membrane. Before this preliminary treatment can be extended 

 and applied to ex])erimental data, it will be worthwhile to discuss these 

 problems so that they may point the direction to an improvement of the 

 theory. 



100 



0.01 



O.OOi- 



0.0001 h 

 CONC. 

 (mM) 



Fig. 14-17. Variation of the intracellular inhibitor concentration and the in- 

 ternal pH with the external pH (scheme 14-150). The cells are unbuffered with 

 an initial pH,- of 6.8. (Ij)^ = 10 mM, Z„ = 10-^ and (H)» = 1.6 X 10-' M. 



The Bulk Intracellular pH 



Determinations of intracellular pH have been made for the past 50 

 years with a variety of techniques and under greatly different conditions of 

 the cells. The results of different workers have often shown discrepancies, 

 which is not surprising considering that some of the techniques for meas- 

 uring the pH (e.g., the use of dye indicators) are subject to large errors and 

 that any deviation in the state of the tissue from normalcy leads to rapid 

 and marked changes in the pH. The recent development of micro-pH- 



