Dissociation of the inhibitory activities of iodoacetamide (IAc) on specific histamine release and lactate production in human leucocytes.

The occasional but repeated failure of iodoacetamide (IAc) to inhibit histamine release led to a detailed study of the effect of this inhibitor on human leucocytes. When histamine release (HR) and lactate production (LP) were both determined on aliquots of dextran-sedimented cells, HR was inhibited to a much greater extent than LP. In contrast, leucocytes fractionated on Isopaque—Ficoll or with glass beads produced cell populations which were readily inhibited by IAc in both HR and LP. Addition of IAc to fractionated cells 4 minutes after antigen resulted in inhibition of lactate production but no depression of HR. These results indicate that there is a dissociation of specific histamine release and lactate production in human leucocytes and that inhibition by IAc occurs early in the process of histamine release.