Comparative study of glucocorticoid sensitivity and receptors in lymphoid tissues

Abstract

Glucocorticoid sensitivity of different lymphoid tissues of avian and mammalian origin was investigated. As a measure of glucocorticoid effect variation of thymidine kinase activity was selected. By this method an order of sensitivity was established among various species and tissues. Dexamethasone uptake by isolated lymphocytes and specific binding to cytosol receptors was also examined. No direct correlation was found between glucocorticoid sensitivity and either binding capacity (receptor number per cell) or affinity of receptor for hormone. The presence of one homogeneous binding site was detected in each tissue examined both by isolated cell technique and cytosol saturation analysis in the range of 1–40 nM of [ 3H]-dexamethasone concentration. In all cases about 80% of the bound dexamethasone was associated with cell nucleus in our system. Dexamethasone binding of the hydrocortisone resistant subpopulation of chicken lymphoid tissues was studied after in vivo treatment with high doses of hydrocortisone. The surviving cells contained an amount of dexamethasone receptor cell similar to that of the whole population. A theoretical analysis of the steady-state receptor cycle gives an explanation for the differences between the values of K A determined in intact cells or in cellfree systems.