Glucocorticoid binding to normal and activated alveolar lung cells.

Abstract

The presence of specific, high affinity, low capacity glucocorticoid binding was demonstrated in resident and activated rabbit lung macrophage suspensions. The binding of [3H]-dexamethasone reached a plateau after 2 h at 30° C. Scatchard analysis revealed only a single class of binding sites in both activated and nonactivated macrophages. There was no significant difference in the dissociation constants for the binding of dexamethasone to nonactivated and activated macrophages (4.39 ± 2.53 × 10−9 vs. 1.08 ± 0.36 × 10−9 M). The number of binding sites in activated macrophages (15,900 ± 1,710 binding sites per cell), however, was significantly greater than the number of binding sites in nonactivated macrophages (5,260 ± 490 binding sites per cell). The relative binding activities of steroids for the receptor were dexamethasone ≌ triamcinolone acetonide > cortisol > corticosterone > progesterone ≌ testosterone > 17β-estradiol. Thus, a specific glucocorticoid receptor exists in nonactivated and activated lung macrophages. The presence of activation is associated with a large increase in the number of specific glucocorticoid binding sites per cell.