Determination of intracellular pH by color film histophotometry of frozen in situ rat brain.

Abstract

Regulation of intracellular pH (pHi) is a critical factor in brain function in normal and pathological states. An inability to maintain controlled pHi during and after conditions which impose severe metabolic stress on the brain has been implicated as contributory to permanent neurologic damage in severe hypoxia, ischemic stroke, and seizures (1,2). The relationship between energy metabolism and pHi has been difficult to study because of spatial and temporal heterogeneity in brain physiology. Furthermore, there is a lack of effective techniques for determining pHi in brain which are compatible with concurrent measurement, or control, of other variables which affect or reflect cell physiology. For example, tissue lactate levels have been considered to reflect pHi, but this relationship has not been verified by direct experimental determination. The quantitative method for determining tissue lactate, which also preserves spatial distribution, excludes most existing techniques for quantitative pH measurement. This problem might be resolved by the use of colorimetric pH indicator dyes. The requirements for an in vivo colorimetric pH indicator in the mammalian central nervous system are stringent, but can be met by the vital dye neutral red (3).