Sex differences in adrenocortical structure and function. I. The effects of postpubertal gonadectomy and gonadal hormone replacement on nuclear volume of adrenocortical cells in the rat

Development of sexual dimorphism of skeletal muscles through the adrenal cortex, caused by androgen-induced global gene suppression

The zona fasciculata (zF) in the adrenal cortex contributes to multiple physiological actions through glucocorticoid synthesis. The size, proliferation, and glucocorticoid synthesis characteristics are all female biased, and sexual dimorphism is established by androgen. In this study, transcriptomes were obtained to unveil the sex differentiation mechanism. Interestingly, both the amount of mRNA and the expressions of nearly all genes were higher in females. The expression of Nr5a1, which is essential for steroidogenic cell differentiation, was also female biased. Whole-genome studies demonstrated that NR5A1 regulates nearly all gene expression directly or indirectly. This suggests that androgen-induced global gene suppression is potentially mediated by NR5A1. Using Nr5a1 heterozygous mice, whose adrenal cortex is smaller than the wild type, we demonstrated that the size of skeletal muscles is possibly regulated by glucocorticoid synthesized by zF. Taken together, considering the ubiquitous presence of glucocorticoid receptors, our findings provide a pathway for sex differentiation through glucocorticoid synthesis.

Enduring sex-dependent effects of lipopolysaccharide treatment on the hypothalamic-pituitary-gonadal axis in mice

Pubertal stress causes enduring sexual behavior dysfunction in males and females, but the underlying mechanism remains unknown. These changes may arise from pubertal programming of the hypothalamic-pituitary-gonadal axis. Previous findings show that stress exposure downregulates the hypothalamic-pituitary-gonadal axis, particularly through the reduction of the neuropeptide kisspeptin (Kiss1) and its receptor (Kiss1R). Although acute changes in kiss1 and Kiss1r genes have been observed following pubertal immune stress, it is unclear whether immune stress-induced downregulation of kiss1 and kiss1r persists beyond puberty. The current study investigated the enduring sex-specific consequences of lipopolysaccharide on the expression of Kiss1 and Kiss1r in 160 pubertal or adult mice at multiple time points. Six-week and 10-week-old male and female mice were treated with either saline or with lipopolysaccharide. Mice were euthanized either 8 h or 4 weeks following treatment. Although we did not identify any sex differences, our results revealed that lipopolysaccharide treatment decreases hypothalamic Kiss1 and Kiss1r in both pubertal and adult mice within 8 h of treatment. The decreased hypothalamic Kiss1 expression persists 4 weeks later only in mice treated with lipopolysaccharide during puberty. Our findings highlight the age-dependent vulnerability of the hypothalamic-pituitary-gonadal axis to immune stress, providing a better understanding of the mechanisms implicated in allostatic shift during immune stress. Finally, our findings also show the effects of immune stress on various components of the hypothalamic-pituitary-gonadal axis, which could have implications for sexual and fertility-related dysfunctions.

Sex-Dependent Pathology in the HPA Axis at a Sub-acute Period After Experimental Traumatic Brain Injury

Over 2.8 million traumatic brain injuries (TBIs) are reported in the United States annually, of which, over 75% are mild TBIs with diffuse axonal injury (DAI) as the primary pathology. TBI instigates a stress response that stimulates the hypothalamic-pituitary-adrenal (HPA) axis concurrently with DAI in brain regions responsible for feedback regulation. While the incidence of affective symptoms is high in both men and women, presentation is more prevalent and severe in women. Few studies have longitudinally evaluated the etiology underlying late-onset affective symptoms after mild TBI and even fewer have included females in the experimental design. In the experimental TBI model employed in this study, evidence of chronic HPA dysregulation has been reported at 2 months post-injury in male rats, with peak neuropathology in other regions of the brain at 7 days post-injury (DPI). We predicted that mechanisms leading to dysregulation of the HPA axis in male and female rats would be most evident at 7 DPI, the sub-acute time point. Young adult age-matched male and naturally cycling female Sprague Dawley rats were subjected to midline fluid percussion injury (mFPI) or sham surgery. Corticotropin releasing hormone, gliosis, and glucocorticoid receptor (GR) levels were evaluated in the hypothalamus and hippocampus, along with baseline plasma adrenocorticotropic hormone (ACTH) and adrenal gland weights. Microglial response in the paraventricular nucleus of the hypothalamus indicated mild neuroinflammation in males compared to sex-matched shams, but not females. Evidence of microglia activation in the dentate gyrus of the hippocampus was robust in both sexes compared with uninjured shams and there was evidence of a significant interaction between sex and injury regarding microglial cell count. GFAP intensity and astrocyte numbers increased as a function of injury, indicative of astrocytosis. GR protein levels were elevated 30% in the hippocampus of females in comparison to sex-matched shams. These data indicate sex-differences in sub-acute pathophysiology following DAI that precede late-onset HPA axis dysregulation. Further understanding of the etiology leading up to late-onset HPA axis dysregulation following DAI could identify targets to stabilize feedback, attenuate symptoms, and improve efficacy of rehabilitation and overall recovery.

Sex-related gene expression profiles in the adrenal cortex in the mature rat: microarray analysis with emphasis on genes involved in steroidogenesis

Notable sex-related differences exist in mammalian adrenal cortex structure and function. In adult rats, the adrenal weight and the average volume of zona fasciculata cells of females are larger and secrete greater amounts of corticosterone than those of males. The molecular bases of these sex-related differences are poorly understood. In this study, to explore the molecular background of these differences, we defined zone- and sex-specific transcripts in adult male and female (estrous cycle phase) rats. Twelve-week-old rats of both genders were used and samples were taken from the zona glomerulosa (ZG) and zona fasciculata/reticularis (ZF/R) zones. Transcriptome identification was carried out using the Affymetrix^® Rat Gene 1.1 ST Array. The microarray data were compared by fold change with significance according to moderated t-statistics. Subsequently, we performed functional annotation clustering using the Gene Ontology (GO) and Database for Annotation, Visualization and Integrated Discovery (DAVID). In the first step, we explored differentially expressed transcripts in the adrenal ZG and ZF/R. The number of differentially expressed transcripts was notably higher in the female than in the male rats (702 vs. 571). The differentially expressed genes which were significantly enriched included genes involved in steroid hormone metabolism, and their expression levels in the ZF/R of adult female rats were significantly higher compared with those in the male rats. In the female ZF/R, when compared with that of the males, prevailing numbers of genes linked to cell fraction, oxidation/reduction processes, response to nutrients and to extracellular stimuli or steroid hormone stimuli were downregulated. The microarray data for key genes involved directly in steroidogenesis were confirmed by qPCR. Thus, when compared with that of the males, in the female ZF/R, higher expression levels of genes involved directly in steroid hormone synthesis were accompanied by lower expression levels of genes regulating basal cell functions.

Central ghrelin treatment stimulates ACTH cells in normal-fed, food-restricted and high-fed rats: An immunohistomorphometric and hormonal study

Changes in feeding regime represent serious stress, while ghrelin is considered a key player in energy balance. We investigated the effects of intracerebroventricular (ICV) ghrelin application on pituitary adrenocorticotropic (ACTH) cells in rats fed diets differing in energy content. Before the ICV treatment, male Wistar rats were subjected to three different feeding regimes for 4 weeks: normal-fed (NF), food-restricted (FR) or high-fed (HF) (n = 3 × 14). At the age of 8 weeks, rats from each group were divided into two subgroups and given ICV, either ghrelin (G; 1 μg ghrelin/5 μl PBS, n = 7) or solvent alone (5 μl PBS, n = 7) every 24 h for 5 days. The immunohistochemical appearance and quantitative morphology of pituitary ACTH cells were evaluated, as well as peripheral ACTH and corticosterone levels. Central ghrelin administration increased (p<0.05) ACTH cell volumes in GNF, GFR and GHF rats by 8.1%, 11.8% and 9.1%, respectively, compared to the controls, while significant increases in ACTH cell volume density were observed in GNF and GHF rats. Circulating ACTH and corticosterone levels were elevated (p<0.05) in GNF and GFR rats by 72.8% and 80.8%, respectively, when compared to the corresponding controls. Thus, central ghrelin administration stimulated the pituitary-adrenal axis under preserved and negative energy balance states.

Pregnancy reduces the responsiveness of the pituitary-adrenal axis to dexamethasone

This study aimed to examine the influence of pregnancy on responsiveness of the pituitary-adrenal (PA) axis to dexamethasone (Dx) in rats. Dams and virgins were injected with Dx in three consecutive daily doses of 1.0, 0.5, 0.5mg/kg/bw, starting from day 16 of pregnancy, and sacrificed 24 and 72 h after termination of treatment. Immunocytochemical, morphometrical and biochemical methods were used to assess pituitary and adrenal function. Three-way ANOVA revealed Dx inhibition of the PA axis in virgin and pregnant females after 24 and 72 h. Pregnant females demonstrated a significantly lower (p<0.05) degree of suppression regarding ACTH volume density and blood concentrations and the volume and number of the zona fasciculata and zona reticularis cells, comparing with virgin females 72 h following Dx administration, accompanied by total recovery of the zona glomerulosa. In contrast to virgin females, the corticosterone levels on day 21 of gestation reached control levels. Between days 19 and 21 of pregnancy, a significant increase in estrogen levels and the fall of progesterone influence, at least partially, the presented differences. It can be concluded that the PA axis response to the inhibitory influence of Dx is less pronounced in gravid females during late pregnancy than in virgin rats.

Effect of acute heat stress on rat adrenal cortex — a morphological and ultrastructural study

The stereological structure of rat adrenal gland was analysed by light and electron microscopy after an acute (60 min) exposure to high ambient temperature (38°C). Under these conditions a significant increase in plasma corticotrophin (ACTH), serum corticosterone and aldosterone levels were observed. Histological and stereological investigation at light microscopy showed significant decrease in volume density of capsule and zona glomerulosa, increase in volume of fasciculata cells, and decrease of numerical density of zona fasciculata cells and mean diameter of blood vessels. At the ultrastructural level, volume density of nuclei and mitochondria of zona glomerulosa cells were significantly increased and that of lipid droplets decreased. Volume density of mitochondria of fasciculata cells was significantly increased, while number of lipid droplets per µm2 of cell was reduced. In the cells of zona reticularis significant increase in the number of lipid droplets was found. The response of zona glomerulosa may be interpreted as immediate reaction to dehydration, while alterations detected in zona fasciculata, which were less extensive, were related to purely stressogenic effects of high ambiental temperature.

The adrenal cortex in female rats after estradiol or calcium treatment

Administration of estradiol or calcium, or combined, represents the classical therapeutic approach in the treatment of some menopausal symptoms. We have studied the effects of estradiol dipropionate (EDP) and calcium glucoheptonate (Ca) on morphological and hormonal features of the adrenal gland in 14-month-old female Wistar rats. The animals were treated with EDP (0.625 mg/kg b.w.) or Ca (11.4 mg/kg b.w.) daily for two weeks, with control rats receiving vehicle alone by the same schedule. The cell volumes in the zona glomerulosa (ZG) and zona fasciculata (ZF) were 11.2% and 5.5% greater (P<0.05) and in the zona reticularis (ZR) 13.0% smaller (P<0.05) in the EDP group than in the control group. In the Ca group, cell volume in the ZG was increased by 5.6% (P<0.05), while cell volumes in the ZF and ZR were decreased by 26.0% and 14.7%, respectively (P<0.05), in comparison with control values. Serum aldosterone and corticosterone concentrations were higher in the EDP-treated (by 27.8% and 19.8%, respectively) and Ca-treated (by 80.0% and 24.1%, respectively) groups in comparison with the control group (P<0.05). These data suggest that EDP and Ca treatments have stimulatory effects on the ZG and ZF, but inhibitory effects on the ZR in middle-aged female rats.

The effect of centrally administered ghrelin on pituitary ACTH cells and circulating ACTH and corticosterone in rats

Ghrelin is a brain-gut peptide known for its growth hormone (GH)-releasing and appetite-inducing activities. This natural GH secretagogue (GHS) was originally purified from rat stomach, but it is expressed widely in different tissues where it may have endocrine and paracrine effects. The central effects of ghrelin on adrenocorticotropic hormone (ACTH) cells, ACTH release and subsequent corticosterone release from adrenal glands remains to be clarified. The aim of this study was to specifically determine the morphological features of ACTH-producing pituicytes and blood concentration of ACTH and corticosterone after central administration of ghrelin. Five doses of rat ghrelin or PBS (n=10 per group) were injected every 24 h (1 microg of ghrelin in 5 muL PBS), into the lateral cerebral ventricle of male rats. Results showed that ghrelin increased (p<0.05) absolute and relative pituitary weights compared to controls (58% and 41% respectively). Morphometric parameters, i.e. the volume of the ACTH cells, nuclear volume, and volume density were all increased (p<0.05), by 17%, 6% and 13%, respectively, 2 h after the last ghrelin treatment. Ghrelin increased circulating concentrations of ACTH and corticosterone (p<0.05) by 62% and 66%, respectively. The data provide clear documentation that intracerebroventricular ghrelin stimulates ACTH cell hypertrophy and proliferation, and promotes ACTH and corticosterone release. Determining the role of ghrelin in physiological stress responses and whether control of the peptide's activity would be useful for prevention and/or treatment of stress-induced diseases remain important research goals.

The pituitary-adrenal axis of fetal rats after maternal dexamethasone treatment

Elevated glucocorticoid level in the gravid female circulation affects number of endocrine functions in fetuses and offspring. In this research female rats were injected with dexamethasone (Dx) in three consecutive daily doses of 1.0, 0.5, 0.5 mg/kg body weight, starting from day 16 of pregnancy. The influence of this treatment on the pituitary adrenocorticotrophic (ACTH) cells and adrenal glands of 19-day-old fetuses was examined immunocytochemically and by morphometric analysis. Moreover, the proliferative activity of adrenocortical cells was estimated after application of the mitotic inhibitor Oncovine. Administration of Dx to pregnant rats induced a decline of fetal ACTH cell immunopositivity and significant decreases of ACTH cell volume (23%, p < 0.05), volume density (41%, p < 0.05), and its number per unit area (17%, p < 0.05) in comparison to the control 19-day-old fetuses. Reduced proliferative activity of adrenocortical cells (31%; p < 0.05) in zona glomerulosa, as well as the volume of this zone were detected. The volume and number of fetal adrenocortical cells in the inner zone and chromoblasts were not significantly reduced after Dx treatment of pregnant rats. These results show that maternal Dx administration in the period when the fetal hypothalamo-pituitary-adrenal (PA) axis begins its function inhibited the PA axis. Reduced ACTH cell function and mitotic activity led to suppression of adrenocortical cell multiplication in zona glomerulosa, the region of the adrenal cortex where most proliferating cells were found in control 19-day-old fetuses. Thus, increased glucocorticoid levels during late pregnancy caused developmental modifications involving the fetal PA axis, which could be the basis of the altered endocrine responsiveness in adult life.

ACTH-producing cells of 21-day-old rat fetuses after maternal dexamethasone exposure

Adrenocorticotrophic hormone (ACTH) is essential for developmental maturation of numerous organ systems during the fetal period and for adaptation to environmental challenges. Immunocytochemical and stereological methods were used in the present study to examine the effects of dexamethasone (Dx) administration during pregnancy on fetal rat pituitary ACTH-producing cells. Doses of 0.5, 0.5 and 1.0 mg Dx/kg body weight/day were given to the dams on 3 consecutive days starting on day 16 of gestation. Morphometric analysis of the ACTH-producing cells of fetuses at 21 days of gestation revealed significant inhibition by 24% and 27%, respectively, of cell volume and cell number after maternal Dx administration, whereas the volume of cell nuclei and volume density of ACTH-stained cells were insignificantly decreased. Immunocytochemical analysis showed reduced numbers, sizes and immunopositivity of ACTH cells of 21-day-old fetuses from Dx-treated dams as compared with the control group. Maternal Dx treatment in the period of intense differentiation of the hypothalamo-hypophyseal-adrenal system had an inhibitory effect on fetal function and proliferative activity of ACTH-producing cells at 21 days of gestation. Thus, inhibition of activity of fetal ACTH-producing cells may lead to adrenal suppression, modified activity of the hypothalamo-pituitary-adrenal axis and reduced body weight possibly causing lasting functional abnormalities.

Prolactin induces adrenal hypertrophy

Although adrenocorticotropic hormone is generally considered to play a major role in the regulation of adrenal glucocorticoid secretion, several reports have suggested that other pituitary hormones (e.g., prolactin) also play a significant role in the regulation of adrenal function. The aim of the present study was to measure the adrenocortical cell area and to determine the effects of the transition from the prepubertal to the postpubertal period on the hyperprolactinemic state induced by domperidone (4.0 mg kg-1 day-1, sc). In hyperprolactinemic adult and young rats, the adrenals were heavier, as determined at necropsy, than in the respective controls: adults (30 days: 0.16 +/- 0.008 and 0.11 +/- 0.007; 46 days: 0.17 +/- 0.006 and 0.12 +/- 0.008, and 61 days: 0.17 +/- 0.008 and 0.10 +/- 0.004 mg for treated and control animals, respectively; P < 0.05), and young rats (30 days: 0.19 +/- 0.003 and 0.16 +/- 0.007, and 60 days: 0.16 +/- 0.006 and 0.13 +/- 0.009 mg; P < 0.05). We selected randomly a circular area in which we counted the nuclei of adrenocortical cells. The area of zona fasciculata cells was increased in hyperprolactinemic adult and young rats compared to controls: adults: (61 days: 524.90 +/- 47.85 and 244.84 +/- 9.03 microm2 for treated and control animals, respectively; P < 0.05), and young rats: (15 days: 462.30 +/- 16.24 and 414.28 +/- 18.19; 60 days: 640.51 +/- 12.91 and 480.24 +/- 22.79 microm2 ; P < 0.05). Based on these data we conclude that the increase in adrenal weight observed in the hyperprolactinemic animals may be due to prolactin-induced adrenocortical cell hypertrophy.

Peptide growth factors and the adrenal cortex

Increasing evidence suggests that the actions of classical stimulants of adrenocortical growth and function, such as ACTH or dietary sodium restriction, may partially be mediated via locally produced regulators. Several peptide growth factors, such as basic fibroblast growth factor, insulin-like growth factors, and transforming growth factor-beta 1, have emerged in recent years as multifunctional molecules that typically play such regulatory roles. Adrenocortical cells are highly responsive to these growth factors, in particular in the regulation of cell growth and differentiated functions, such as steroidogenesis. In addition, growth factor expression in the adrenal cortex has been shown to be regulated by physiological stimulants. The spatial expression, release, and activation of these growth factors may, therefore, locally mediate or amplify the actions of the hypothalamo-pituitary axis and the renin-angiotensin system on adrenocortical proliferation, differentiation, and steroidogenesis.

Long-term effects of ovariectomy on pituitary-adrenal axis and specific antibody response in rats

The effects of ovariectomy on morphologically demonstrable characteristics of lymphoid tissue, pituitary, and adrenal glands as well as on plasma ACTH and corticosterone levels and humoral immunity of female Lewis rats were investigated. The present study establishes ovaries as potential regulatory organs upon thymus, pituitary, and adrenal glands in female Lewis rats. In addition to the effects on these important lymphoid organs and endocrine glands, ovariectomy influenced the time course of serum IgM antibody titres against fluorescein isothiocyanate (FITC), but had only moderate effects upon serum IgG antibody titres. In conclusion, the present results suggest that ovariectomy modifies morphological characteristics of the thymus and pituitary-adrenal axis. Furthermore, circulating corticosterone seems to play an important role in regulating antibody formation in intact compared to ovariectomized female Lewis rats, while the influence of thymic mass is far from clear.

Sex differences in adrenocortical structure and function. XXII. Light- and electron-microscopic morphometric studies on the effects of gonadectomy and gonadal hormone replacement on the rat adrenal cortex

The cytological aspects of sexual dimorphism in the rat adrenal cortex and its relationship to the gonads have been investigated. The adrenal glands of mature female rats were heavier than those of males, and morphometry showed that this was almost exclusively due to conspicuous differences in the volume of cells of the zona fasciculata (ZF) and zona reticularis (ZR). Stereology demonstrated that the volume of the mitochondrial and lipid droplet compartments, as well as the surface area per cell of mitochondrial cristae and smooth endoplasmic reticulum tubules, were markedly higher in the ZF and ZR cells of female animals. Orchiectomy increased and ovariectomy decreased the adrenal weight, by eliciting hypertrophy and atrophy, respectively, of ZF and ZR cells; these effects of gonadectomy were reversed by the appropriate gonadal hormone replacement. It is suggested that the sexual dimorphism of the rat adrenal cortex may depend upon the inhibitory action of testosterone and the stimulatory effect of estradiol on the hypothalamo-hypophyseal-adrenal axis.

Sex differences in adrenocortical structure and function. XII. Stereologic studies of rat adrenal cortex in the course of maturation

This paper reports a stereological study of the cellular aspects of development of the adrenal cortex of male and female rats in the course of maturation. Rats of the Wistar strain were studied at weekly intervals from day 21 to day 77 of postnatal life. From day 42 homogenates of adrenals from female rats produced more corticosterone than homogenates from males of corresponding age. In the strain of rats studied sex differences in adrenal weight appeared at about day 49. From this day onward relative, and subsequently absolute adrenal weights were higher in females than in males. In the course of maturation the total volume of all adrenocortical zones gradually increased. From day 70 the zona glomerulosa and from day 49 the zona fasciculata were larger in female than in male rats, while no distinct sex difference was observed in the volume of the zona reticularis. The appearance of sex-related differences in the adrenal cortex depends mainly on changes in the zona fasciculata, the cells of which markedly increased in volume in female rats by comparison with males. The total number of all adrenocortical cells increased from ca 13 million on day 21 to ca 25 million on day 77 and at all intervals studied adrenal glands of male and female rats contained a similar number of parenchymal cells.

Sex differences in adrenocortical structure and function. XI. Autoradiographic studies on cell proliferation and turnover in the adrenal cortex of the male and female rat and its dependence on testosterone and estradiol

Adrenal glands from orchectomized and ovariectomized rats, with and without replacement therapy, and also from intact controls of both sexes, were examined by autoradiography with 3H-thymidine. The labelling index after 1 or 2 nucleoside injections was higher in the zona glomerulosa of females than in male rats, while no differences were found in the fascicular and reticular zones. Orchiectomy increased the labelling index in the fascicular and reticular zones, an effect prevented by testosterone. Ovariectomy did not change the labelling index, while estradiol lowered it in the zona glomerulosa. Duration of the S phase was longer in the zona fasciculata cells of males than in females. Both orchiectomy and testosterone shortened this phase in cells of the zona fasciculata and zona reticularis. Ovariectomy prolonged the S phase in the zona fasciculata and shortened this time in the reticular zone, an effect reversed by estradiol. In the glomerular and fascicular zones, cell cycle time was longer in males than in females. Orchiectomy shortened this time in all adrenocortical zones, an effect reversed by testosterone. Ovariectomy shortened cell cycle time in the glomerular and reticular zones and prolonged it in the zona fasciculata; these effects were reversed by estradiol. Turnover rate in adrenocortical cells was markedly higher in females than in males, a difference due to testosterone which markedly decreased turnover rate.