Histamine, 5-hydroxytryptamine and compound 48/80 activate PMN-leucocyte collagenase of the rat

Experimental pleurisy in rat and intraperitoneal injection of histamine, serotonin and the histamine releaser compound 48/80 caused changes in blood leucocyte populations. An increased number of PMN-leucocytes was observed. The peripheral blood PMN-leucocytes of non-treated rats contained collagenase mainly in the latent form. During experimental pleurisy and after treatment with histamine, serotonin and compound 48/80 activation of latent collagenase of up to 90-98% was obtained. Mepyramine, cimetidine and timegadine inhibited activation of latent collagenase by compound 48/80. It is suggested that histamine is involved in the process of activation of leucocyte collagenase in the course of inflammation.