EFFECTS OF ENDOCRINE MANIPULATIONS ON OESTROGEN BINDING IN CYTOSOLS FROM RAT SKELETAL AND PERINEAL MUSCLES

Hormonal regulation of cytosolic oestradiol-binding sites in the levator ani bulbocavernosus (LA/BC) muscles of male rats and in thigh muscles from male and female rats was investigated. Twenty-four hours after gonadectomy and/or adrenalectomy, the number of unoccupied oestradiol-binding sites was significantly increased in cytosols prepared from LA/BC muscles while these treatments had no effect on thigh muscles from male rats. Only a combination of both treatments led to a significant increase of oestradiol-binding sites in cytosols prepared from the thigh muscles of female rats when compared with those of intact rats at dioestrus. The number of oestradiol-binding sites in the thigh muscles of female rats was found to vary during the oestrous cycle with values significantly lower at pro-oestrus than at dioestrus. The increase in oestradiol-binding sites observed in cytosols prepared from muscles of adrenalectomized or gonadectomized plus adrenalectomized rats was prevented by an injection of corticosterone (3 mg, s.c.) at the time of surgery. Twenty-one days after gonad and/or adrenal ablation, the mean concentration of oestradiol-binding sites in the three tissues under study was higher than in these tissues from intact rats, and in some groups the levels of oestradiol-binding sites were significantly higher than they had been 24 h after the same surgical treatments. Muscles from male rats hypophysectomized for 28 days possessed levels of oestradiol-binding sites equivalent to male rats deprived of steroid hormones for 21 days. Dexamethasone treatment of male rats (100 μg/day for 14 days) led to a progressive decrease of oestradiol-binding sites of LA/BC and thigh muscles. This study has shown that adrenal and gonadal hormones exert both short- and long-acting repressive effects on the oestradiol-binding capacity of rat muscles.