Effects of acute injection of methylprednisolone in man on immunological and non-immunological histamine release from leucocytes and its potentiation by interleukin-3.

We investigated the effects of intravenous injection of methylprednisolone (MPR) compared with placebo (saline) on ex vivo leucocytic histamine release in eight healthy volunteers. All subjects received in a randomized and a single-blind manner the placebo and MPR, 20 mg and 125 mg, each injection given in 2 week intervals. On each occasion blood samples were taken just before and 24 h after the intravenous injection to determine circulating leucocyte counts and leucocytic histamine release induced by anti-IgE (1/2000) and FMP (Formyl-Methionyl-Phenylalanine) (10(-5) M) and its modulation by IL-3 (2 ng/ml). MPR 20 mg and 125 mg significantly increased circulating leucocyte counts (P < 0.05 and P < 0.001 respectively) but decreased leucocytic histamine content (P < 0.05 and P < 0.001 respectively) by 24 h. Placebo had no effect. As for circulating basophils, after 24 h they were decreased by 125 mg MPR (P < 0.05) but increased by 20 mg (P < 0.05). Anti-IgE-induced HR was significantly inhibited by 125 mg MPR (P < 0.05) but not by 20 mg MPR or by the placebo. In contrast, neither MPR (20 mg and 125 mg) nor placebo significantly reduced FMP-induced HR. The strong potentiation by IL-3 of HR evoked by anti-IgE and FMP at baseline (P < 0.001) persisted 24 h after injection of MPR or placebo (P < 0.001 except P < 0.05 for anti-IgE-induced HR after 125 mg MPR).(ABSTRACT TRUNCATED AT 250 WORDS)