Similar Actions of Glucocorticoids and Calcium on the Regulation of Apoptosis in S49 Cells

Glucocorticoid-induced lymphocyte cell death is a programmed process which is thought to involve the calcium-dependent degradation of DNA into multiples of 180 basepairs, characteristic of internucleosomal degradation. We have used the glucocorticoid- sensitive mouse lymphoma cell line S49.1 [wild-type (wt)] and the glucocorticoid-resistant cell line S49.22r (nt−) to evaluate the role of both glucocorticoid receptors and calcium in the regulation of internucleosomal DNA degradation and expression of calcium-dependent deoxyribonuclease activity. DNA was isolated from untreated (control) and dexamethasone (dex)-treated viable cells and analyzed for internucleosomal DNA degradation by agarose gel electrophoresis, followed by ethidium bromide staining. Glucocorticoid treatment resulted in substantial internucleosomal DNA degradation in wt cells, but not in nt− cells. This effect was inhibited by coincubation of cells with dex and the glucocorticoid receptor antagonist RU486. In contrast to the glucocorticoid ...