Effect of hypophysectomy on corticotropin-releasing hormone and adrenocorticotropin immunoreactivities in the rat adrenal gland.
It has previously been shown that rat adrenal zona medullaris possesses an interleukin-1 beta (IL-1 beta)-responsive peripheral branch of the CRH/ACTH system that duplicates the hypothalamopituitary central one (Mazzocchi et al., Mol. Cell. Neurosci. 4: 267, 1993). The intraadrenal content of corticotropin-releasing hormone (CRH) and adrenocorticotropin (ACTH) immunoreactivities (ir), as well as IL-1 beta-stimulated release of CRH-ir and ACTH-ir, increased in relation to the number of days elapsed from hypophysectomy; the effect of hypophysectomy required at least 48 h to become significant and reached its maximum after 72 h. The action of IL-1 beta on ACTH-ir release was annulled by simultaneous exposure to alpha-helical-CRH, an antagonist of CRH. ACTH infusion, at a rate restoring a normal blood level of the hormone, prevented the effect of hypophysectomy on intraadrenal concentrations of both CRH-ir and ACTH-ir; similarly, the hypophysectomy-evoked rise in intraadrenal ACTH-ir content was completely annulled by treating hypophysectomized rats with CRH or dexamethasone. Taken together our findings suggest that the elimination of the central branch of CRH/ACTH system induces a marked increase in the activity of the intraadrenal peripheral one. The hypothesis is advanced that the hypophysectomy-induced lowering of circulating ACTH and the consequent drop in the production of adrenal glucocorticoids enhances, via a classic negative feedback mechanism, gene expression of CRH and ACTH in adrenal medullary chromaffin cells.
Mazzocchi
G
G
Department of Anatomy, University of Padua, Italy.
Malendowicz
L K
LK
Markowska
A
A
Nussdorfer
G G
GG
D000313:Adrenal Medulla / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis* / Q000494:pharmacology; D000818:Animals; D003345:Corticosterone / Q000502:physiology; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis* / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005246:Feedback; D005786:Gene Expression Regulation; D007016:Hypophysectomy; D007375:Interleukin-1 / Q000494:pharmacology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D007375:Interleukin-1; C069206:alpha helical corticotropin-releasing hormone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone