INJURY OF RAT THYMOCYTES CAUSED BY EXOGENOUS PEROXYL RADICALS IN-VITRO

The aim of this study was to investigate oxidative cell injury in rat thymocytes under conditions of radical generation exterior to the cell utilizing the thermolabile azocompound 2,2'-azobis(2-amidinopropane) dihydrochloride to generate peroxyl radicals at a constant and reprodu cible rate. This initiator, being water-soluble and endowed with a pos itive charge, is suitable for studies on oxidative damage of biomembra nes induced in the external water environment. The relationship betwee n cell viability, lipid and thiol oxidation and chain-breaking antioxi dant depletion was studied. During the first hour of treatment cell vi ability decreased slightly, protein sulfhydryl groups were consumed sl owly and no significant production of conjugated dienes occurred. Afte r 90 min of incubation, when thymocyte permeability started to increas e, the concentration of alpha-tocopherol decreased gradually, signific ant changes of polyunsaturated fatty acids occurred and a rapid phase of thiol oxidation commenced. It can be concluded that, under conditio ns of an exogenous oxidant challenge, initially the cell membrane prov ides a physical barrier to the entrance of radicals to the thymocyte. When peroxyl radicals gain access to the membrane and the molecular ba rrier begins to disorganize, the oxidizable cellular components become susceptible to massive attack.