The present experiments show, however, that X-zone regression can be stimulated in the ovariectomized unmated female or in the castrated male by subcutaneous injections of adrenocorticotrophic hormone, indicating that androgens are produced by the adrenals themselves. Jones concludes 6, after a long series of investigations, that these androgens are derived from the ovaries under the stimulation of placental gonadotrophins. 8) The sex hormones from the adrenal cortex are primarily androgens. Only androgens among purified hormones do this, so it is generally agreed that male hormones must circulate in the pregnant mouse.
In the normal male, therefore, endogenous androgens cause regression of the zone and in both the castrated male and the virgin female exogenous androgens have the same effect 4,5. A similar zone disappears in the male mouse before maturity but persists or redevelops after immature or adult castration. THE transitory inner cortical X-zone of the virgin female mouse first described and illustrated by Masui and Tamura 1 and later by Howard-Miller 2, Deanesly 3 and many others, regresses rapidly during the first pregnancy and only gradually in the unmated female.
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