DIFFERENCES IN VAGINAL SENSITIVITY OF MICE OF INBRED STRAINS; LOCALIZATION IN THE VAGINA1

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Abstract
THE vaginal mucosa of mice of different inbred strains differs in responsiveness to exogenous estrogen (1, 2, 3, 4). More than four times as much estrogen was required to induce cornification in 50% ± 10% of the vaginas of mice of some strains than was required by mice of other strains (4, 5). The differences in vaginal sensitivity were not correlated with susceptibility to mammary cancer (1, 3, 4, 6). The strain differences in susceptibility of the vaginal mucosa may be due to the genetic constitution of mice of the different strains which result in (a) differences in the rate of inactivation or excretion of injected estrogen, (b) differences in the production of estrogen or substances that might antagonize or augment their action, or (c) differences in the responsiveness of the end organ. The possibility that differences in inactivation or excretion of the hormones might occur was excluded largely when the topical application of the hormones to the vaginal mucosa revealed a similar order of the responses although with much smaller amounts of estrogen (5). The possibilities mentioned under items (b) and (c) above, however, could not be elucidated by such experiments.