Abstract
Physiological effect of two major ovarian hormones, estradiol and progesterone, was examined on the uptake of 3H-leucine in the brains of ovariectomized adult rats. The animals ovariectomized previously were divided into 4 groups as follows according to the subsequent hormonal treatments, group 1; control animals, group 2; animals treated with estradiol benzoate plus oil, group 3; animals treated twice with estradiol benzoate, and group 4; estradiol benzoate-primed animals treated with progesterone. Animals in each group were given a single se injection of 3H-leucine 2 hr after the last hormonal treatment. Animals were sacrificed 2hr after the injection. Intensity of the uptake of 3Hleucine was measured by counting the number of reduced silver grains over cells in various brain regions, using an autoradiographic technique.
Group 1 showed a relatively high uptake in SO and PV, as compared with that in the remaining hypothalamic regions. Group 2 slightly induced an enhancement of the uptake in SO and PV, but not in the remaining hypothalamic regions, as compared with that in group 1. Group 3 showed a signifiant enhancement of the uptake in all the hypothalamic regions except PVA, as compared with that in groups 1 and 2. Group 4 enhanced significantly the uptake in all the hypothalamic nuclear regions except PV and MM, as compared with that in groups 1 and 2. The uptake in cells of the cerebral cortex and ependyme remanined unchanged after hormonal treatments in groups 2, 3 and 4.
The present results suggest that two major hormones stimulate protein synthesis in most of the hypothalamic nuclear regions, but not in the cerebral cortex and the ependyme. It is also suggested that, in connection with protein synthesis in the hypothalamus, response of the hypothalamus to progesterone is not affected by estrogen-priming. A possible role of both hormones in their positive feed-back control of the hypothalamus was discussed, with special reference to gonadotrophin releasing factors produced in the hypothalamus.
