ABSTRACT
The effect of progesterone on pituitary gonadotrophin release has been studied in the rat. Castrated female rats bearing ovarian autotransplants, or unilaterally ovariectomized rats, were given 1 to 5 mg of progesterone daily for intervals from 7 to 28 days, and then killed. The ovaries, uteri, and vaginas were examined grossly and microscopically, and the pituitary glands were assayed for total gonadotrophin content by the mouse uterine weight method.
Although treatment with 5 mg of progesterone for 28 days inhibited ovulation, it did not prevent Graafian follicle development (determined histologically) or secretory function (evaluated by the presence of vaginal mucification) in either of the animal preparations. Progesterone treatment was associated with a significant elevation of pituitary gonadotrophic potency in the castrated rats bearing ovarian autotransplants, but not in the unilaterally ovariectomized rats.
These findings suggest that the tonic rate of gonadotrophin secretion is unaffected by treatment with 5 mg of progesterone daily. The acute discharge of the ovulation inducing hormone complex (probably primarily LH) is, however, inhibited by such a dose of progesterone, and probably accounts for the inhibition of ovulation. The findings also suggest that the amount of progesterone secreted by the functioning corpora lutea during pseudopregnancy in the rat is equivalent in effect to between 2 and 5 mg of progesterone injected once daily.
SMAD3 regulates the diverse functions of rat granulosa cells relating to the FSHR/PKA signaling pathway
