Effects of actinomycin on in vivo and in vitro formation of endogenous rabbit pyrogen induced with myxoviruses or stimulated with endotoxin

Summary The synthesis of virus-induced endogenous pyrogen and of interferons is inhibited by actinomycin both in rabbits and in exudate granulocytes from the peritoneal cavities of rabbits; the degree of inhibition is a function of the administered dose. The process involves an intracellular inhibition of pyrogen synthesis rather than a blocking of its release from the cell. Only in extracts from controls not treated with actinomycin it proved possible to trace endogenous pyrogen.However, when bacterial endotoxin is used as a stimulus, neither the formation of endogenous pyrogenin vivo norin vitro is influenced by actinomycin. It is known that the same also applies to endotoxin-induced Interferon synthesis.One may assume that in order to generate virus-induced endogenous pyrogen and Interferon,de novo protein synthesis is required. The endogenous pyrogen found in consequence to endotoxin stimulation, however, appears to be present in the cells in a pre-formed state. In a similar way to that of interferons it is apparently released upon administration of the stimulus.Actinomycin had a moderate blocking effect on the formation of thermic pyrogen in exudate granulocytes.Supported by the Deutsche Forschungsgemeinschaft.