[Changes in the level of epidermal G2-chalone and mitotic activity in the rat vaginal epithelium]

The content of tissue-specific inhibitor of mitosis in epidermal epithelium (G2-chalone) was estimated by a single radial immunodiffusion test in the rat vagina during various stages of the estrous cycle. The level of chalone was found to correlate with the mitotic index (MI) of vaginal epithelium. The lowest level of G2-chalone is detected in proestrus and the highest one in estrus. The level of G2-chalone in vaginal epithelium was shown to be significantly decreased in aging rats (14--16 month-old) with regular cycles as compared to that in young normal cycle rats (3--4 month-old). The single injection of estradiol benzoate (1 microgram/100 g) into ovariectomized rats led to an increase in the MI following 18 hours. The increased MI is preceeded by a substantial drop of the G2-chalone level 12 hours after estrogen injection.