Estrogen-like stimulation of uterine ornithine decarboxylase by cholera toxin

Cholera toxin administered by intrauterine injection to ovariectomized rats increased uterine ornithine decarboxylase activity as much as systemic estradiol at 4 h after treatment. At 45-60 min after treatment, however, cholera toxin did not increase nuclear estrogen receptor or stimulate synthesis of the uterine "induced protein," which is closely correlated with nuclear receptor, whereas estradiol caused substantial increases in both nuclear receptor and induced protein synthesis. Intrauterine injection of cholera toxin also produced an estrogen-like elevation of the uterine protein/DNA ratio at 24 h. Because both cholera toxin and estradiol are known to increase vascular permeability, our results support the hypothesis that some uterine effects of estradiol are not mediated by receptor-genome interaction but involve another mechanism that is associated with increased vascular permeability.