Radiation-induced apoptosis in thymocytes: pH sensitization.

Thymocytes were used as a model system to study the effect of microenvironmental pH changes on the radiation-induced apoptosis. We found that the sensitivity of thymocytes toward radiation induced apoptosis is increased by increasing the pH of the incubation medium. The major sensitivity change occurs between pH 7 and 8. In a given cell suspension the results obtained where similar when the apoptosis evaluation was carried out either by counting the picnotic nuclei, or monitoring the fraction of apoptotic nuclei by flow cytometry; both methods show a radiosensitization when the pH value of incubation media rises from 7 to 8. These results may be important when "in vitro" experiments are performed with lymphoid cells, since changes in pH of the media may determine important changes in the results.