Effect of sympathomimetic amines on the histamine forming capacity of human leucocytes.

1 The effects of alpha- and beta-adrenoceptor stimulants on the histamine-forming capacity (HFC) of human isolated leucocytes have been studied, in vitro.2 It was confirmed that antigen significantly stimulates the HFC of human leucocytes.3 beta-Adrenoceptor stimulants, such as isoprenaline and salbutamol (10(-6)-10(-3)M) significantly inhibited the HFC of human leucocytes in the presence and absence of antigen. At concentrations lower than 10(-6)M, this effect was not observed. In general the degree of inhibition of HFC by beta-adrenoceptor stimulants followed their potency as beta-adrenoceptor stimulants.4 alpha-Adrenoceptor stimulants significantly stimulated leucocyte HFC; noradrenaline within a limited concentration of 10(-6)M, while stimulation was seen consistently with phenylephrine at concentrations of 10(-7)-10(-4)M. Adrenaline, which stimulates both alpha- and beta-adrenoceptors, produced small inhibition, no effect, or a degree of stimulation.5 Phentolamine, an alpha-adrenoceptor blocking agent, produced an effect opposite to that of the alpha-adrenoceptor stimulants, i.e. a significant inhibition of the HFC of human isolated leucocytes.