Gender-dependent characteristics of the hypothalamo-corticotrope axis function in glucocorticoid-replete and glucocorticoid-depleted rats.
The aim of the present study was to determine the role of the endogenous sex steroid environment in the hypothalamo-corticotrope (HC) function in both sham-operated (SHAM) and bilaterally adrenalectomized (ADX) rats. For this purpose adult rats of both sexes were used 3 and 6 weeks after either SHAM or ADX. The results indicate that: a) in SHAM animals, basal plasma ACTH levels were significantly higher in females than in males, and this sexual dimorphism was overridden by ADX, regardless of the time post-surgery; b) although basal anterior pituitary (AP) ACTH content was similar in SHAM animals of both sexes, 3- and 6-week ADX induced higher AP ACTH in males than in females; c) at 3- and 6-weeks, ADX rats of hoth sexes had an AVP:CRH ratio (r), in the median eminence (ME) and medial basal hypothalamus (MBH), increased several fold over the respective SHAM-value and, although no sexual dimorphism was found at week 3 post-ADX, by 6-weeks post ADX, these ratios were significantly higher in both brain tissues of females than in those of males; and d) the in vitro ME CRH and AVP output in response to high potassium concentrations (hK+; 28 and 56 mmol/I), was concentration-related, regardless of sex and surgery, and was characterized by enhanced secretion of neuropeptides by MEs from ADX in comparison to SHAM rats of both sexes, and a sexual dimorphism was found in this parameter, consisting in general, in greater neuropeptide output from tissues of female than of male animals. Our results indicate that: 1) there is a gender-dependent characteristic of the HC axis function in glucocorticoid-replete rats and 2) the absence of the glucocorticoid negative feedback mechanism is responsible for either the expression or for the override of the sexual dimorphism in different parameters, a phenomenon which dependent on the time elapsed after ADX.
Chisari
A N
AN
School of Exact Sciences, UNLP, La Plata, Argentina.
Perone
M J
MJ
Giovambattista
A
A
Spinedi
E
E
D000302:Adrenal Cortex / Q000502:physiology*; D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000032:analysis; D003346:Corticotropin-Releasing Hormone / Q000032:analysis; D005260:Female; D005938:Glucocorticoids / Q000172:deficiency* / Q000502:physiology; D007031:Hypothalamus / Q000737:chemistry / Q000502:physiology*; D007033:Hypothalamus, Middle / Q000737:chemistry; D008297:Male; D008473:Median Eminence / Q000737:chemistry / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics