Effect of corticosterone and dexamethasone on glucocorticoid receptor in lactating rat mammary gland.
The effects of either a single dose or long-term administration of corticosterone or dexamethasone 21-acetate (Dex Ac) on glucocorticoid receptor concentration in mammary gland cytosol of lactating adrenalectomized rats were investigated. Adrenalectomy on lactation day 7 failed to affect the glucocorticoid receptors significantly. Both the natural and synthetic steroid caused a rapid decrease of receptor binding in the cytosol but the time course of glucocorticoid receptor depletion was different. Complete depletion of cytosol receptor was observed after both a single s.c. Dex Ac dose (20 micrograms/100 g) and after long-term oral treatment (10 micrograms/ml saline as drinking solution for 6 days) immediately after the last steroid dose. In the first case the depletion was still observable at 24 h after the injection without any change in Kd. In contrast, prolonged administration of Dex Ac maintained the receptor binding low even for 48 h after steroid withdrawal and resulted in an increased Kd. Even after an additional day the binding did not exceed the level of 50% of controls. By that time, however, Kd has returned to normal values. On the other hand, a single dose of corticosterone (100 micrograms/100 g) as well as long-term corticosterone treatment (100 micrograms/ml saline as drinking solution for 6 days) reduced the glucocorticoid receptor concentration only to 60% and 25%, respectively. Twenty four hours after the hormone administration the receptor binding returned to control level, no change in Kd being observed. It was concluded that Dex Ac, but not corticosterone, down-regulates the glucocorticoid receptors in mammary gland cytosol of lactating rats.
Alexandrová
M
M
Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, CSFR.
D000315:Adrenalectomy; D000818:Animals; D003345:Corticosterone / Q000008:administration & dosage / Q000494:pharmacology*; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005260:Female; D007267:Injections; D007774:Lactation / Q000187:drug effects*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000187:drug effects*; D013997:Time Factors
D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D003345:Corticosterone