Acute and subacute effects of dexamethasone on the number of white blood cells in rats

The purpose of this study was to elucidate the effects of dexamethasone, a synthetic glucocorticoid, on the immune system by analyzing the number of white blood cells (WBCs) over the course of hours and days of dexamethasone administration. Dexamethasone was given as either a single dosage [1.0mg/kg body weight (BW); subcutaneous injection (s.c.)] or as a daily dosage (1.0mg/kg BW per day; s.c.) for 10 days for the hourly and daily assessment of changes in the number of white blood cells, respectively. A single administration of dexamethasone markedly decreased the number of total WBCs, as well as the number of lymphocyte, monocyte, neutrophil and eosinophil subsets with a nadir at 8 hr post-injection. The number of these cells recovered to the control levels at 24hr. The numbers of total WBCs, lymphocytes, monocyte, eosinophil and basophil were reduced by the daily administration of dexamethasone. However, the number of neutrophil was significantly higher at days 2 and 8 after the injection. These results suggest that glucocorticoid-mediated immunosuppressions are at least partly attributable to quantitative changes in the number of circulating WBCs.