Increase in incorporation into lymphocytes in vitro of esterified anti-inflammatory corticosteroids.

Corticosteroids esterified at C-17 and C-21 such as hydrocortisone 17-butyrate 21-propionate (HBP) and prednisolone 17-valerate 21-acetate (PVA) inhibited PHA-induced blastogenesis of human blood lymphocytes more intensively than hydrocortisone (HC) and prednisolone (PSL), the parent corticosteroids. When lymphocytes were incubated with HBP or HC, the total amount of HBP incorporated into lymphocytes was much larger than that of HC. The amount of HBP bound specifically to the receptors was also increased, which may be due to the increased concentration of corticosteroid in lymphocytes. These results suggest that the increased incorporation of the esterified corticosteroids into cells would be most important to produce an intensive biological activity.