PREDNISOLONE PHARMACODYNAMICS - LEUKOCYTE TRAFFICKING IN THE RAT

Leukocytes circulate throughout the body patrolling for foreign antige ns and facilitating immune responses. Corticosteroids exert their immu nosuppressive actions, in part, by inhibiting the normal trafficking o f these cells. The rat was used to investigate corticosteroid-induced changes in circulating total lymphocytes, CD4(+) cells, and granulocyt es. Prednisolone doses of 5, 25, and 50 mg/kg or saline were given iv. Blood was taken over 24 hr for analysis of cell subsets by flow cytom etry. Steroid exposure was assessed by assaying plasma prednisolone by HPLC. Response profiles were complicated, possibly by opposing effect s on the recirculation of cells to blood. This prospect was investigat ed using pharmacodynamic cell trafficking models. Steroid-like effects in saline treated animals that may be due to stress or other factors limited data interpretation. As an animal model to characterize cell t rafficking actions, the rat is an imperfect model.