CALCULATION OF INTRACELLULAR pH FROM THE DISTRIBUTION OF 5,5-DIMETHYL-2,4-OXAZOLIDINEDIONE (DMO). APPLICATION TO SKELETAL MUSCLE OF THE DOG*

Abstract

Estimations of hydrogen ion activities in the interior of cells have been attempted through a number of different experimental approaches. The methods that have been employed are of several general types: measurements on preparations of broken cells, measurements on fluid withdrawn from cells, observations with visible indicators, measurements with micro-electrodes introduced into cells, measurements of the intracellular and extracellular concentrations of weak organic acids and bases, and calculation of the balance of ionic charges. The last named method has been proposed by Conway (1). The other methods are discussed in the review of Caldwell (2), which contains a tabulation of the results of measurements on various types of cells with different experimental methods. Some of the methods that have been used are of quite limited applicability, and most of the values arrived at by any of the methods are subject to question. Potentially, the method utilizing the distribution of weak organic acids and bases has a wider range of applicability than the other methods, and it is not subject to some of the theoretical objections that can be raised to other methods. There is a great deal of evidence that membranes of animal and plant cells in general are characterized by free permeability to the undissociated forms of weak organic acids and bases and by impermea