RELEASE OF HISTAMINE IN WHOLE-BLOOD BY OXYGEN RADICALS - DIVISION BETWEEN SPECIFIC AND UNSPECIFIC PROCESSES

Oxygen derived free radicals are involved in many pathological process es such as postischemic reperfusion injuries: hepatotoxicity of drugs and inflammatory processes. Thereby these oxygen radicals induce lipid peroxidation and perturbation of cellular membranes. The aim of our p resent study was to determine whether oxygen radicals generated by the xanthine oxidase/hypoxanthine system cause a release of histamine in human blood cell cultures. Stimulation of blood cell cultures with oxy gen radicals induced a histamine liberation which was mainly due to ca lcium independent processes during the first 30 min, whereas then calc ium requiring processes took part in the release of histamine. The reg ulation of the leukocyte selectin LECAM-1 was altered by oxygen radica ls whereas histamine, which is known to modulate vascular selectin exp ression, did not affect the expression of LECAM-1. Our data indicate t hat oxygen radicals induce a direct calcium independent release of his tamine which is due to membrane pertubating processes during the first phase but also induce a specific reaction leading to a further indire ct histamine liberation which is probably mediated by PAF.