Oestrogens down-regulate type I but not type II adrenal corticoid receptors in rat anterior pituitary.
We have studied type I and type II adrenal cortical steroid receptors in the anterior (AL), intermediate (IL) and posterior (PL) lobes of the pituitary and in the hippocampus of ovariectomized-adrenalectomized female rats and in castrated-adrenalectomized male animals, with or without oestrogen treatment. Using [3H]dexamethasone as ligand and conditions suitable for determination of its binding to type I and type II receptors, we found that 4 or 15 days of oestrogen reduced type I receptors in AL by 50-60% without changes in IL, PL or hippocampus, or in type II sites in any of the four neuroendocrine tissues studied. This down-regulatory effect was seen only in female rats and no change was found for males. The reduction in type I sites in AL in oestrogenized female rats was confirmed by labelling type I sites with the synthetic antimineralocorticoid [3H]ZK 91587. Saturation analysis with [3H]ZK 91587 demonstrated that the reduction was due to a reduction in Bmax without change in Kd. We conclude that: (a) type I receptors in the anterior pituitary are under oestrogenic control; (b) there is a sex difference in the response to oestrogen of AL type I sites; and (c) this demonstration may be useful in determining the role of type I receptors in neuroendocrine regulation of the anterior pituitary by hormones derived from the adrenal cortex, and the participation of sex hormones in this process.
Ferrini
M
M
Laboratorio de Bioquímica Neuroendócrina, Instituto de Biología y Medicina Experimental, Buenos Aires, Argentina.
Magariños
A M
AM
De Nicola
A F
AF
D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002369:Castration; D003907:Dexamethasone / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008901:Mineralocorticoids / Q000037:antagonists & inhibitors; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D018043:Receptors, Corticotropin; D011979:Receptors, Pituitary Hormone / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D012737:Sex Factors; D013148:Spironolactone / Q000031:analogs & derivatives / Q000378:metabolism
D008901:Mineralocorticoids; D018043:Receptors, Corticotropin; D011979:Receptors, Pituitary Hormone; D013148:Spironolactone; D004958:Estradiol; D003907:Dexamethasone; C054537:ZK 91587; D000324:Adrenocorticotropic Hormone