Regulation of mitotic activity in rat vaginal epithelium: relationships between the level of its inhibitor (G2-chalone) and estrogens.
The level of a tissue-specific inhibitor of mitotic activity (G2-chalone) and mitotic activity in the vaginal mucosa of cycling rats of varying age and castrated rats were studied. A direct correlation between the level of the inhibitor and mitotic index is found in cycling animals. Both parameters are maximal during estrus and minimal in proestrus, when estrogen level in blood circulation is the highest. The undulating variations in G2 inhibitor level during estrous cycle are less pronounced and the concentrations of the inhibitor in relevant phases are significantly lower in aged females than in adult rats. Administration of estradiol benzoate (1 microgram/100 g) to castrated female rats was followed by a significant decrease in mitotic inhibitor level in vaginal mucosa within 12 hrs. This, in turn, was followed by a rise in mitotic activity 18 hr after estrogen administration. Therefore, the estrogen exerts its effect on mitotic activity in target tissue after it has induced a decrease in the level of the antimitotic factor (G2-chalone).
D000818:Animals; D002369:Castration; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D004958:Estradiol / Q000097:blood / Q000494:pharmacology; D004971:Estrus / Q000187:drug effects; D005260:Female; D006131:Growth Inhibitors / Q000502:physiology*; D008938:Mitosis / Q000187:drug effects; D008940:Mitotic Index / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D014621:Vagina / Q000187:drug effects / Q000502:physiology*
D006131:Growth Inhibitors; D004958:Estradiol