Influence of histamine H-antagonists on human leukocytes.

To determine the role of the histamine H-receptor on basophils, different specific H-antagonists were investigated. Incubation of washed leukocytes with N-acylated histamine-derivatives (N-ahd) induced elevated histamine levels. This process turned out to be dependent on dose, time and temperature, but independent of Ca and Mg ions. IgE-mediated histamine release was not modulated. [H]- l-histidine was not decarboxylated into [H]-histamine in spite of the observed histamine increase. Highly purified basophils did not show any histamine elevation but purified neutrophils and eosinophils were found to have increased histamine levels even after disintegration and subsequent incubation with N-ahd. It seems that the increased histamine levels result from the cleavage of the applied histamine amides. Other potent H-antagonists (e.g. thioperamide) neither produced increased histamine levels nor influenced IgE-mediated release from basophil leukocytes. The existence of H-receptors on human basophils therefore seems unlikely. [ABSTRACT FROM AUTHOR]