Identification of Potassium-Dependent and -Independent Components of the Apoptotic Machinery in Mouse Ovarian Germ Cells and Granulosa Cells

Abstract Recent studies with thymocytes have suggested a critical role for intracellular potassium in the regulation of apoptosis. In this study, we examined the pathways of K+ regulation during ovarian cell death. In initial studies, fluorographic analysis demonstrated a significant loss of K+ during apoptosis stimulated by doxorubicin in oocytes and trophic hormone deprivation in granulosa cells. In oocytes, suppression of potassium efflux by potassium-enriched medium prevented condensation, budding, and fragmentation, although it did not block DNA degradation, suggesting the existence of potassium-independent nucleases in oocytes. Culture of granulosa cells in potassium-enriched medium inhibited internucleosomal DNA cleavage, although high-molecular weight DNA cleavage was apparent, suggesting that the nuclease or nucleases responsible for generating 50-kilobase (kb) fragments in these cells is potassium independent. To address this directly, isolated granulosa cell nuclei were stimulated to autodigest...