MECHANISM OF ACTION OF MEDROXYPROGESTERONE (17α-ACETOXY-6α-METHYL PROGESTERONE) IN THE RAT

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ANANT P. LABHSETWAR
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Summary.

In an attempt to characterize the effects of medroxyprogesterone (17α-acetoxy-6α-methyl progesterone) more precisely, the compound was administered subcutaneously to immature rats twice a week (12·5 mg/injection) for 5 weeks. The effects of medroxyprogesterone on the pituitary gland were evaluated by measuring the lh content of the gland by the method of Parlow, while those on the ovaries were studied by measuring the ovarian response to exogenous pms (10 i.u.). In the treated animals there were significant decreases in ovarian, uterine, adrenal, pituitary and body weights; corpora lutea were absent and vaginal opening was delayed. The ovarian response to pms was not decreased. There was a significant decline in both concentration and total gland content of lh due to treatment.

It is suggested that the major action of medroxyprogesterone, when administered for an extended period of time in the doses used, is exerted at the pituitary level. It blocks the synthesis of LH in the pituitary gland without affecting ovarian sensitivity to gonadotrophins.

 

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