Early effects of corticosteroids on basophils, leukocyte histamine, and tissue histamine.

The comparative effect in 11 atopic subjects of a single intravenous injection of methylprednisolone on sequential studies of blood eosinophils, basophils, leukocyte sensitivity to antigen for histamine release, leukocyte histamine content, and skin histamine was examined. No significant changes occurred in any parameter after placebo treatment. In contrast, 4 hr after intravenous treatment with steroid there were significant decreases in mean eosinophil counts (-95%), basophil counts (-72%), and histamine content of 1 X 10(7) leukocyte samples (-62%). Temporal changes in the latter paralleled alterations in circulating basophil levels. No significant changes occured in the antigen histamine release sensitivity, or the total skin histamine. Studies over a longer period after steroids in 4 subjects showed eosinophil and basophil levels at a nadir at 8 hr, remaining suppressed for 24 hr, and returned to pretreatment levels by 72 hr. Results suggest that corticosteroids induce a prominent decrease in leukocyte histamine due to a depletion of basophils without a decrease in histamine content per basophil, and that skin tissue histamine stores remain unchanged by such treatment.