High intracellular pH accompanies mitotic activity in murine lymphocytes

Intracellular pH is crucial to the control of many cellular processes such as glycolysis, protein synthesis, and cell division. To study the relation between intracellular pH and mitotic activity in actively dividing Con A- or LPS-stimulated splenic lymphocytes, a method was developed to determine intracellular pH using a fluorescence-activated cell sorter. The new method uses the pH-sensitive fluorochrome, 4-methylumbelliferone. Results obtained with it not only correspond qualitatively with the results obtained using 14C-dimethyloxazolidinedione (DMO) but also clearly show the active and inactive subpopulations. The intracellular pH of mitogen-stimulated murine lymphocytes increases from pH 7.15 to pH 7.45 when the population has greatest mitotic activity. The intracellular pH of three virus-transformed lymphocyte cell lines is higher by approximately 0.5 pH units when the cells are in exponential growth compared to stationary phase.