Changes in the level of epidermal G2 chalone and mitotic activity in the vaginal epithelium of rats

The content of epidermal inhibitor of mitosis (G₂ chalone) at different stages of the estrous cycle in rats was determined by the radial immunodiffusion method. The chalone level correlates with the mitotic index of the vaginal mucous membrane and is minimal in proestrus and maximal in estrus. In aging (14–16 months) rats with regular cycles the content of G₂ chalone in the vaginal mucous membrane at all phases of the estrous cycle was significantly lower than in young (3–4 months) rats with a regular cycle. In castrated rats the mitotic index begins to rise 18 h after a single injection of estradiol benzoate (1 g/100 g body weight). This increase is preceded by a significant decrease in the concentration of G₂ chalone 12 h after injection of the estrogen.Laboratory of Experimental Tumors and Laboratory of Endocrinology, N. N. Petrov Research Institute of Oncology, Ministry of Health of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR A. I. Serebrov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 87, No. 4 pp. 349–351, April, 1979.