[Blood estradiol level and G2-chalone content in the vaginal mucosa in rats of different ages].

17 beta-Estradiol level was higher in the blood serum of rats aged 14 to 16 months with regular estral cycles during all the phases as compared to that in 3- to 4-month-old female rats. The latter ones had a higher vaginal mucosa G2-chalone concentration. The level of the vaginal mucosa G2-chalone decreased in young rats 12 hours after subcutaneous benzoate-estradiol injection (1 micrograms/100 g body weight) to ovariectomized animals but increased in 14- to 16-month-old female rats. One year following ovariectomy the vaginal mucosa G2-chalone level was lower than in young and aged female rats 2 weeks after surgery. Possible role of age-associated disturbances of the regulatory cell proliferation stimulant (estrogen) and its inhibitor (chalone) interactions in neoplastic target tissue transformation is discussed.