Inhibition of inducible liver enzymes by endotoxin and actinomycin D

Berry, L. Joe (Bryn Mawr College, Bryn Mawr, Pa.), Dorothy S. Smythe, and Louise S. Colwell. Inhibition of inducible liver enzymes by endotoxin and actinomycin D. J. Bacteriol. 92:107-115. 1966.-Bacterial endotoxin at the ld(50) level lowers liver tryptophan pyrrolase in mice, it prevents for 16 to 20 hr the induction of the enzyme by a concurrent injection of cortisone, it lowers significantly but does not prevent substrate induction, and it reduces the enzymatic activity promptly and significantly when administered during the course of hormonal induction. The ld(50) amount of actinomycin D has a similar effect on tryptophan pyrrolase, except that its inhibition of induction by cortisone persists for a longer period of time. Endotoxin in the intact mouse induces tyrosine-alpha-ketoglutarate transaminase almost as well as cortisone, but not in the adrenalectomized animal, a fact that suggests induction of this enzyme is due to release of endogenous adrenal hormones. Actinomycin D, on the other hand, has an effect on this transaminase similar to that on tryptophan pyrrolase. The site of action of endotoxin and actinomycin D would appear to be similar for one of the two enzymes studied and different for the other, a relationship that requires a specificity difficult to imagine for a material as complex as endotoxin.