Objective To investigate the effect of endogenous glucocorticoids on the immune function of macrophages and their dose-effect or time-effect relationship.    Methods The peritoneal macrophages obtained from male SD rats were stimulated with corticosterone (10

50

100

500

1000 ng/ml) for different time period. Then the innate immunity of macrophages was evaluated

such as adherence

Chemotaxis

phagocytic capacity and the ability to secret TNF-α.    Results Corticosterone (50 ng/ml) enhanced adherence and phagocytic ability of macrophages (P0.05) and their ability to secret TNF-α (P0.01). Corticosterone （10 ng/ml and 50 ng/ml） enhanced Chemotaxis of macrophages (P0.05). When stimulated by 500 or 1000 ng/ml corticosterone

the immune function of macrophages was depressed or not influenced. Within the time period of stimulation from 0.5 to 5 h

the corticostetone treatment for 1 h could improve the phagocytic function and TNF-α secretion of peritoneal macrophages

but longer stimulation suppressed this effect.   Conclusion Acute stimulation of endogenous glucocorticoids at a certain dosage can enhance the immune function.