Modulation of glucocorticoid hormone receptor levels in chicken lymphoid tissue following treatment with androgens in vivo

Abstract

Lymphatic tissues are highly sensitive to androgens and androgens are thought to contribute to sex differences in the immune response. In this study we have examined the effects of androgens on cytosolic glucocorticoid receptor levels in lymphoid tissues. The immature chick was chosen for our experimental model because it allows the separate evaluation of the bursa of Fabricius (primarily B-cells) compared to the thymus (primary T-cells). Treatment with dihydrotestosterone (a potent androgen in chicks) for 3–12 days in vivo reduced the cytosolic glucocorticoid (triamcinolone acetonide-[ 3H]) receptors in the bursa tissue to ∼ 42% of control levels after 5 days and ⩽ 5% of control levels after 7 days of treatment. The chick thymus tissues were still ~ 92% of control triamcinolone acetonide receptor levels after 5 days of androgen treatments. However, the thymus levels had dropped to ⩽ 5% of control values after 12 treatment days. Thus a difference in the rate of decrease in the bursa of Fabricius compared to the thymus was indicated. The blastogenesis index (BI), a measurement of the percentage of cells progressing through the cell cycle, was figured using fluorescent DNA staining with diamidino phenylindole followed by flow cytomctry analysis. After 3, 5, or 7 days of androgen treatment, the bursa of Fabricius from dihydrotestosterone treated chicks (2 mg/day/chick) had a mean BI = 11.17 (±3.07 SD) which was significantly lower than the bursa of Fabricius from control chicks which showed a mean BI = 27.33 (±3.42 SD). The thymus from dihydrotestosterone treated chicks had a mean BI = 19.57 (±2.19 SD) which was slightly but not significantly higher than the control thymus BI = 17.38 (±0.89 SD). In summary, androgen treatment in vivo induced a decrease in the cytosolic glucocorticoid hormone receptor levels in both the chick thymus and bursa of Fabricius tissues while decreasing the blastogenesis index in the bursa cells but not in the thymus cells.