REGULATION OF UTERINE G6PD MESSENGER-RNA LEVELS IN THE RAT UTERUS BY ESTRADIOL - REQUIREMENT OF PROTEIN-SYNTHESIS FOR MESSENGER-RNA INDUCTION

Estradiol (E2) increases uterine glucose-6-phosphate dehydrogenase (G6PD) by increasing the synthesis of the C6PD mRNA, increasing the rate of mRNA translation, increasing pre-G6PD processing, and increasing enzyme stability. The time course and magnitude of changes in total uterine C6PD mRNA in ovariectomized mature rats after E2 treatment, and the effects of actinomycin D and cycloheximide on the induction of G6PD mRNA levels by E2 were examined. Total uterine RNA was subjected to Northern analysis using a 2.8 kb insert from a rat uterine G6PD cDNA clone to probe the blots. Relative amounts of G6PD mRNA were determined by densitometric comparison of autoradiogram bands corresponding to G6PD mRNA. Uterine RNA contains a 2.5 kb RNA that hybridized with the G6PD cDNA. Total G6PD mRNA levels increased 3, 10, 15 and 5-fold above control values at 6, 12, 24 and 48 h after a single dose of E2, respectively. Actinomycin D given with E2, or cycloheximide given within 4 h after E2, inhibited E2 induction of G6PD mRNA. Actinomycin D given with or without E2 to animals that had received three prior daily injections of E2 to maximally increase endogenous G6PD mRNA levels, caused G6PD mRNA to decrease by 60% by 24 h in both groups indicating that E2 did not stabilize G6PD mRNA. We conclude that E2 induces the levels of uterine G6PD mRNA by a mechanism involving synthesis of a protein(s) within the first 4 h after E2 administration and that E2 does not affect G6PD mRNA stability.