Lymphocytolytic activity of glucocorticoids in vitro: 51Cr release under equilibrium conditions

Cytolytic activity of glucocorticoids in vitro is assessed by measuring radiochromium release from steroid-treated thymic lymphocytes under the equilibrium conditions provided by a continuous-labeling technique. Isotope release is a glucocorticoid-specific effect produced at physiological concentrations and is virtually abolished by inhibitors of RNA and protein synthesis. The relative lytic potencies of the steroids tested are comparable to those reported for glucocorticoids as measured by other methods. This procedure not only possesses the advantages typical of isotopic techniques in general, but, in addition, circumvents the problem of "spontaneous" label release associated with the pulse-labeling method. It is a useful alternative to the morphologic examination of cells or the estimation of cell viability for determination of glucocorticoid cytolytic activity.