Effect of estrogen on synthesis of glucose-6-phosphate dehydrogenase in R3230AC mammary tumors and uteri

Abstract

The effect of estrogen on synthesis of glucose-6-phosphate dehydrogenase ( D-Glucose-6-phosphate: NADP + 1-oxidoreductase, EC 1.1.1.49) in the R3230AC mammary adenocarcinoma of ovariectomized Fischer rats was investigated. Enzyme synthesis was estimated by techniques using immunochemical precipitation and isolation of enzyme protein from tissues of rats that had been given radioactive leucine prior to sacrifice. The antibody-enzyme complex was dissociated and glucose-6-phosphate dehydrogenase was isolated after electrophoresis on sodium dodecyl sulfate-acrylamide gels. Administration of estradiol-17β produced a two-fold increase in glucose-6-phosphate dehydrogenase activity, which was preceded by a five-fold increase in specific synthesis of glucose-6-phosphate dehydrogenase in R3230AC tumors. At least a 15-fold increase in enzyme synthesis was observed in the uterus. The rate of enzyme degradation ( t 1 2 ) in the tumor was estimated at 17 h. These data indicate that the estrogen-induced increase in glucose-6-phosphate dehydrogenase activity was due to a de novo increase in enzyme synthesis.