Rat uterine polyamine biosynthetic decarboxylase activities following multiple injections of estradiol-17B and/or estriol

A single Injection of 0.5 μg estradiol-17B (E2) plus 0.5 μg estriol (E3) stimulated a different pattern in 22–24 day-old rat uterine ornithine decarboxylase (ODC) and S-adenosyl methionine decarboxylase (SAMDC) activities than was Induced by either a single Injection of 0.5 μg E2 or multiple injections of 0.5 μg E3. Differences included alterations in enzyme activity peak timing as well as activity duration. Every 3 hour injections of 0.05 μg E2 induced maximum uterine ODC activity at 4, 24, 32, and 40 hours, intermediate activity at 48, 64, and 72 hours as well as a small peak by 56 hours. When 0.05 μg E2 plus 0.05 μg E3 were injected simitaneously every 3 hours, the ODC activity pattern was similar except that activity fell to intermediate levels by 40 hours. It is suggested that E3 alterations of E2 induced uterine enzyme activities (when monitored at frequent intervals) could be physiological alterations in uterine growth responses due to E2–E3 hormone interactions. However, there appeared to be no differences between E2 or E2 plus E3 Induction of DNA synthesis and luminal epithelial cell height and cross-sectional area or ODC and SAMDC activities when measured at 24, 48, or 72 hours.