Physiological and pathological effects of steroids on the function of the adrenal cortex

Flow-dependent differentiation of cultured adrenal cells under different stimuli

It still remains unclear how the functional organisation of the adrenal cortex arises. One aim of this study was to create a setup which allows for the establishment of a concentration gradient in vitro. This was achieved by a continuous flow of medium through the culture flask which caused differences in glucose and cortisol concentrations as well as in pH values between the sites of inflow and outflow of medium. Using real-time polymerase chain reaction, we found that a continuous supply of 1 ml medium per hour significantly increased the expression of MC2R, CYP11B1 and CYP17A1 genes of NCI-H295R cells in the distal area of the flask as compared with the proximal part. The expression of the AT1R showed a reverse regulation. The addition of dexamethasone to the medium led to an increase in gene expression of MC2R while AT1R was downregulated. Moreover, we detected a higher expression of CYP11B2 and a decreased expression of CYP11B1 when endothelial cell-conditioned medium (ECCM) was added to the inflow. Our experiments show that a directed medium delivery system creates different gradients and affects the functional differentiation of the NCI-H295R cells. Also, our results emphasise that products of endothelial cells have additional effects on the differentiation of the cultured adrenal cortical cells. Our results are in support that the regulation of the adrenal zonation is possible through different concentration gradients.

Endothelial cells regulate β-catenin activity in adrenocortical cells via secretion of basic fibroblast growth factor

Endothelial cell-derived products influence the synthesis of aldosterone and cortisol in human adrenocortical cells by modulating proteins such as steroidogenic acute-regulatory (StAR) protein, steroidogenic factor (SF)-1 and CITED2. However, the potential endothelial cell-derived factors that mediate this effect are still unknown. The current study was perfomed to look into the control of β-catenin activity by endothelial cell-derived factors and to identify a mechanism by which they affect β-catenin activity in adrenocortical NCIH295R cells. Using reporter gene assays and Western blotting, we found that endothelial cell-conditioned medium (ECCM) led to nuclear translocation of β-catenin and an increase in β-catenin-dependent transcription that could be blocked by U0126, an inhibitor of the mitogen-activated protein kinase pathway. Furthermore, we found that a receptor tyrosin kinase (RTK) was involved in ECCM-induced β-catenin-dependent transcription. Through selective inhibition of RTK using Su5402, it was shown that receptors responding to basic fibroblast growth factor (bFGF) mediate the action of ECCM. Adrenocortical cells treated with bFGF showed a significant greater level of bFGF mRNA. In addition, HUVECs secrete bFGF in a density-dependent manner. In conclusion, the data suggest that endothelial cells regulate β-catenin activity in adrenocortical cells also via secretion of basic fibroblast growth factor.

Functional Zonation of the Adult Mammalian Adrenal Cortex

The standard model of adrenocortical zonation holds that the three main zones, glomerulosa, fasciculata, and reticularis each have a distinct function, producing mineralocorticoids (in fact just aldosterone), glucocorticoids, and androgens respectively. Moreover, each zone has its specific mechanism of regulation, though ACTH has actions throughout. Finally, the cells of the cortex originate from a stem cell population in the outer cortex or capsule, and migrate centripetally, changing their phenotype as they progress through the zones. Recent progress in understanding the development of the gland and the distribution of steroidogenic enzymes, trophic hormone receptors, and other factors suggests that this model needs refinement. Firstly, proliferation can take place throughout the gland, and although the stem cells are certainly located in the periphery, zonal replenishment can take place within zones. Perhaps more importantly, neither the distribution of enzymes nor receptors suggest that the individual zones are necessarily autonomous in their production of steroid. This is particularly true of the glomerulosa, which does not seem to have the full suite of enzymes required for aldosterone biosynthesis. Nor, in the rat anyway, does it express MC2R to account for the response of aldosterone to ACTH. It is known that in development, recruitment of stem cells is stimulated by signals from within the glomerulosa. Furthermore, throughout the cortex local regulatory factors, including cytokines, catecholamines and the tissue renin-angiotensin system, modify and refine the effects of the systemic trophic factors. In these and other ways it more and more appears that the functions of the gland should be viewed as an integrated whole, greater than the sum of its component parts.

Practical approaches for evaluating adrenal toxicity in nonclinical safety assessment

The adrenal gland has characteristic morphological and biochemical features that render it particularly susceptible to the actions of xenobiotics. As is the case with other endocrine organs, the adrenal gland is under the control of upstream organs (hypothalamic-pituitary system) in vivo, often making it difficult to elucidate the mode of toxicity of a test article. It is very important, especially for pharmaceuticals, to determine whether a test article-related change is caused by a direct effect or other associated factors. In addition, antemortem data, including clinical signs, body weight, food consumption and clinical pathology, and postmortem data, including gross pathology, organ weight and histopathologic examination of the adrenal glands and other related organs, should be carefully monitored and evaluated. During evaluation, the following should also be taken into account: (1) species, sex and age of animals used, (2) metabolic activation by a cytochrome P450 enzyme(s) and (3) physicochemical properties and the metabolic pathway of the test article. In this review, we describe the following crucial points for toxicologic pathologists to consider when evaluating adrenal toxicity: functional anatomy, blood supply, hormone production in each compartment, steroid biosynthesis, potential medulla-cortex interaction, and species and gender differences in anatomical features and other features of the adrenal gland which could affect vulnerability to toxic effects. Finally practical approaches for evaluating adrenal toxicity in nonclinical safety studies are discussed.

Adrenarche: a cell biological perspective

Adrenarche is a cell biological and endocrinological puzzle. The differentiation of the zona reticularis in childhood in humans requires special techniques for study because it is confined to humans and possibly a small number of other primates. Despite the rapid progress in the definition of adrenocortical stem/progenitor cells in the mouse, the factors that cause the differentiation of adrenocortical cells into zonal cell types have not been identified. There are, however, many candidates in the Wnt, Hedgehog, and other families of signaling molecules. A suitable system for identifying authentic stem cells, capable of differentiation into all zones, has yet to be developed. It is proposed here that the in vitro differentiation of pluripotent cells, combined with appropriate in vitro and in vivo methods for validating authentic adrenocortical stem cells, is a promising approach to solving these questions.

The information provided by the adrenal cortical steroids: a hypothesis

We present the hypothesis that in vertebrates their closed blood circulation facilitated the evolution of the adrenal cortex as a central processing unit that provides the rest of the body with information on the effect of changes in the blood glucose and sodium levels on the functioning of the mitochondria, and of sodium transporters in the adrenal cortex. When cells in the glomerulosa can no longer increase the synthesis of aldosterone, the message to the body is that a higher level of sodium in the blood may damage the cells. When the fasiculata cells cannot increase the synthesis of glucorticoids, the message to the body is that their mitochondria cannot produce more ATP, and that higher levels of glucose in the blood may harm the organism.

Steroid Sulfotransferase 2A1 Gene Transcription Is Regulated by Steroidogenic Factor 1 and GATA-6 in the Human Adrenal

Sulfonation is a phase II conjugation reaction responsible for the biotransformation of many compounds including steroids, bile acids, and drugs. Humans are presently known to express at least five cytosolic sulfotransferase (SULT) enzymes, of which only two are hydroxysteroid SULT, SULT2A1, commonly known as steroid sulfotransferase, and the cholesterol sulfotransferase SULT2B1. SULT2A1 is highly expressed in the adrenal where it is responsible for the sulfation of hydroxysteroids including conversion of dehydroepiandrosterone to dehydroepiandrosterone sulfate and in the liver where it is responsible for sulfation of bile acids and circulating hydroxysteroids. Little is known concerning the transcriptional regulation of human SULT2A1 in adrenal. Herein we demonstrate the role of two transcription factors, steroidogenic factor 1 (SF1) and GATA-6, in the regulation of SULT2A1 transcription. These transcription factors were quantified by real-time RT-PCR in normal human adrenal tissue. Transient transfection assays with deleted and mutated SULT2A1 promoter constructs allowed for the determination of specific SF1 and GATA binding cis-regulatory elements necessary for transactivation of SULT2A1 promoter, and binding was confirmed by EMSA analysis. Both SF1 and GATA-6 were positive regulators of SULT2A1 promoter constructs. These data support the hypothesis that adrenal SULT2A1 expression is regulated by SF1 and GATA-6.

Reactive oxygen disrupts mitochondria in MA-10 tumor Leydig cells and inhibits steroidogenic acute regulatory (StAR) protein and steroidogenesis

Reactive oxygen species (ROS) are involved in a variety of pathophysiological conditions of the testis, and oxidative stress is known to inhibit ovarian and testicular steroidogenesis. The site of ROS-mediated inhibition of steroidogenesis in the corpus luteum and MA-10 tumor Leydig cells was shown to be the hormone-sensitive mitochondrial cholesterol transfer step. The purpose of this study was to examine the effects of ROS on steroidogenic acute regulatory (StAR) protein in MA-10 cells and determine the extent to which MA-10 cell mitochondria are sensitive to oxidative stress. cAMP-stimulated progesterone production was inhibited in a dose-dependent manner in MA-10 cells exposed to H(2)O(2). StAR protein, but not mRNA levels, was decreased in parallel to changes in progesterone production. Even at the highest concentrations of H(2)O(2) tested, there was no effect on P450 side-chain cleavage enzyme protein levels. Oxidative stress from exposure to exogenous xanthine oxidase and xanthine resulted in the inhibition of both progesterone production and StAR protein expression. The mature 30- and 32-kDa intramitochondrial forms of StAR were decreased relative to the 37-kDa extramitochondrial precursor form of StAR, indicating that the ROS-mediated inhibition of StAR protein was due, in part, to the inhibition of mitochondrial import and processing. Vital staining with the fluorescent dye tetramethylrhodamine ethyl ester was used to visualize changes in the mitochondrial electrochemical gradient-dependent membrane potential (Deltapsim). ROS caused a significant dissipation of Deltapsi(m) and time-dependent loss of tetramethylrhodamine ethyl ester fluorescence. The inhibitory effects of H(2)O(2) were transient. There was no evidence for ROS-induced cell death, and following H(2)O(2) removal in the presence of continuous treatment with 8-bromo-cAMP, StAR protein levels and progesterone production were restored. In addition, there was no loss of cell viability following treatment with H(2)O(2) or xanthine/xanthine oxidase as determined by trypan blue exclusion. H(2)O(2) did not cause a significant decrease in total cellular ATP levels. These data indicate that oxidative stress-mediated perturbation of the mitochondria and dissipation of Deltapsi(m) results in the inhibition of StAR protein expression and its import, processing, and cholesterol transfer activity. These findings confirm earlier studies demonstrating the requirement for maintenance of an intact Deltapsi(m) for StAR protein function in cholesterol transport. The significant reduction in the 32- to 30-kDa mature forms of StAR, cessation of cholesterol transport, and loss of Deltapsi(m) are consistent with mitochondrial perturbation because of oxidative stress. This mechanism likely contributes to a host of pathophysiological events evident in testicular disorders such as infection, reperfusion injury, aging, cryptorchidism, and varicocele.

Testicular macrophage modulation of Leydig cell steroidogenesis

This review will highlight recent advances in the study of the immuno-endocrinology of the testis, in particular how macrophage-derived inflammatory mediators affect Leydig cell functions. Both the beneficial and deleterious outcomes resulting from macrophage-Leydig cell interactions are discussed. A brief overview of testicular physiology is provided that discusses the functional and anatomical compartmentalization of the testis into the gamete and endocrine compartments where spermatogenesis and testosterone biosynthesis take place, respectively. The process of steroidogenesis including the activities of the steroidogenic enzymes and the role of steroidogenic acute regulatory protein (StAR) are described. The close physical association between Leydig cells and interstitial testicular macrophages suggests that these cells are functionally related. Under normal physiological and non-inflammatory conditions macrophages play an important role in Leydig cell development. If macrophages are absent from the testicular interstitium, Leydig cells fail to develop normally, which suggest that macrophages provide essential growth and differentiation factors for Leydig cells. In contrast, when macrophages are activated and elaborate inflammatory mediators, Leydig cell steroidogenesis is inhibited. Activated macrophages produce pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor (TNF) that are profoundly inhibitory to Leydig cells and appear to act as transcriptional repressors of steroidogenic enzyme gene expression. Macrophages also produce reactive oxygen species (ROS) such as hydrogen peroxide, which also inhibits Leydig cell functions. ROS appear to act acutely by perturbing Leydig cell mitochondria resulting in the inhibition of StAR protein expression. One important consequence of this immune modulation of Leydig cell function may be manifest behaviorally by switching the affected animal from 'testosterone' behavior, to 'sickness' behavior. Increased interest in immune-endocrine control of reproductive function over the past decade has stimulated research into the molecular and biochemical immunopathophysiology of the reproductive system. As investigations unravel mechanisms underlying reproductive dysfunction caused by inflammation and infection, an understanding of the role that immune-endocrine interactions play in the normal physiology of the reproductive system has emerged.

Influence of insulin and testosterone on adrenocortical steroidogenesis in vitro: preliminary studies

OBJECTIVE

The mechanisms underlying the adrenal androgen (AA) excess of polycystic ovary syndrome (PCOS) remain unclear, although it is possible that the adrenocortical dysfunction may be a response to other, extraadrenal factors. Consistent with the pathophysiology of PCOS and with in vivo data in normal and PCOS women, we have hypothesized that insulin inhibits and that T stimulates AA secretion in vitro.

DESIGN

In vitro experimental study.

SETTING

University medical center.

PATIENT(S)

Normal human adrenals (n = 4 women, ages 25-57 years) were obtained with consent at the time of organ donation.

INTERVENTION(S)

Fresh adrenal tissue minces were incubated in serum-free medium with 10-microM pregnenolone substrate and 1-microM ACTH-(1-24). Challenge doses of 0.2, 1, 5, 20, and 100 nM of insulin and 1, 10, 100, 1,000, and 10,000 nM of T were added, and the media were sampled after 8 hours of incubation at 37 degrees C, 4% CO2. Dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEAS), and cortisol (F) were measured by radioimmunoassay (significant effects compared with the case of zero-dose control).

MAIN OUTCOME MEASURE(S)

The production of DHEA, DHEAS, and F in the media of the adrenal minces was compared between different subjects and at different concentrations of T and insulin.

RESULT(S)

Analysis of the combined data from all donors indicated that insulin stimulated DHEAS and suppressed DHEA production but had no consistent effect on F. Similar analyses of the combined data indicated that T had no significant predictable effect on the production of DHEAS, DHEA, or F. When examining donor data individually, insulin and T did elicit significant increases and/or decreases in steroid production within subjects, although no consistent trends were observed.

CONCLUSION(S)

On the basis of these data, it is clear that extra-adrenal factors such as insulin and T have some adrenal regulatory capacity. In general, insulin stimulated DHEAS and decreased DHEA production, suggesting that it increases adrenocortical sulfotransferase activity. However, although in the individual subjects studied, both insulin and T frequently altered the production of DHEAS, DHEA or F, these effects did not appear to be uniform or consistent from subject to subject. Expanded studies are required to confirm these results.

Intra-adrenal regulation of androgen synthesis

The adrenal cortex encloses the neuroendocrine medulla and is itself subdivided into three distinct zones, each having a specific function and regulation. While the glomerulosa and the fasciculata control vital systems of mineral and energy supply, which are stringently regulated by higher control factors, the function of the reticularis is less clear, beyond supplying a pool of weak androgens, and consequently we do not understand its redundant regulation. The following questions need to be answered: 1. How is the formation of dehydroepiandrosterone (DHEA) and androstenedione differently regulated from glucocorticoid synthesis in normally functioning adrenals? 2. How might growth factors, which increase prepubertally, prime the adrenarche? 3. The regulation of the 17/20-lyase enzyme activity is one of the key factors of adrenal androgen secretion (review [2]). How can the two activities of the P450c17 enzyme be differently regulated in the same cell in a developmentally dependent fashion? This review focuses on the intra-adrenal growth factor system and on the role of 17/20-lyase regulation, as well as on their possible interactions. The increase of activity of the 17/20-lyase enzymatic activity is necessary for the rise of C19 steroids, while the relative increase of formation of DHEA is only possible in the presence of a low 3beta-hydroxysteroid-dehydrogenase (3betaHSD) activity.

Combined 21-hydroxylase and 11beta-hydroxylase deficiency: patient report and molecular basis

A female newborn (46, XX) with ambiguous genitalia was initially diagnosed by biochemical criteria as having classical congenital adrenal hyperplasia caused by 11beta-hydroxylase deficiency. Shortly after effective treatment was administered, she developed a salt-wasting crisis with severe electrolyte imbalance. DNA analysis revealed a homozygous splice mutation in the second intron of the CYP21 gene, for which both parents were heterozygous. No mutations were found in the entire CYP11B1 gene, thus proving that the 11beta-hydroxylase deficiency was not caused by a gene mutation but rather was a secondary event, possibly due to androgen suppression of 11beta-hydroxylase activity.

Hypertension and virilization caused by a unique desoxycorticosterone- and androgen-secreting adrenal adenoma

We describe a rare androgen and desoxycorticosterone (DOC)-secreting adrenal tumor in a non-Cushingoid 14 year-old Haitian girl with secondary amenorrhea, hypertension and virilization. Her steroid pattern simulated an 11 beta-hydroxylation defect with notable elevation of adrenal androgens, 11-desoxycortisol (S), DOC, 17 alpha-hydroxyprogesterone and pregnenelone. Exogenous ACTH stimulated steroidogenesis. A CAT scan unfortunately failed to delineate an adrenal mass. Dexamethasone (DEX) was administered, therefore, which partially suppressed androgen levels, reduced DOC and S by 80% and 82% respectively, and normalized blood pressure. Nevertheless, the response to glucocorticoid was incomplete and an MRI was obtained, which revealed a right adrenal tumor. Post surgery, the patient promptly resumed menses and became normotensive. This case illustrates that ACTH and DEX cannot reliably differentiate tumor from hyperplasia, whereas the simultaneous increase of delta 4 and delta 5 steroids, present here, may favor a tumor. This case also allows speculation that the hypersecretion of DOC may result from inhibition of 11 beta-hydroxylase activity by excess androgens. The importance of appropriate imaging for diagnosis is underscored.

Response of the pituitary-adrenal axis to hypoglycemic stress in women with the polycystic ovary syndrome

The role of the adrenals in the polycystic ovary syndrome (PCOS) is debated. Both single steroid-converting enzyme abnormalities and increased adrenal activity have received support. The conventional Synacthen test using pharmacological doses of ACTH results in unphysiological levels of ACTH. Therefore, we used insulin-induced hypoglycemia (0.15 IU/kg BW) to asses the responses of ACTH, cortisol, pregnenolone, 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone, 17-hydroxyprogesterone, and androstenedione in 18 women with PCOS and in 17 normal women of similar age and body mass index. The blood glucose concentration at 30 min was 2 mmol/L or less in all women, i.e. well below the threshold of the hormonal counterregulatory response. The women with PCOS showed a lower ACTH response, expressed as the maximum increment above basal [mean (95% confidence interval): PCOS, 11.1 (6.9-15.3); controls, 19.9 (13.8-26) pmol/L; P < 0.05], but a quantitatively comparable [PCOS, 207.2 (148.5-266.5); controls, 167.1 (100.6-233.2) nmol/L; P = NS] and more prompt cortisol response than the controls (by chi2 test, P < 0.05), resulting in a higher molar ratio between the maximum increments of cortisol and ACTH [PCOS, 13.9 (8.7-19); controls, 8.8 (5.7-12); P < 0.05]. The women with PCOS did, however, show a more rapid decline in cortisol levels than the controls (P < 0.05 at 120 and 180 min). The responses of the androgens and intermediate adrenal steroids were similar in women with PCOS and controls. The findings suggest an adaptation to increased adrenal reactivity to endogenous ACTH in women with PCOS. Exposure to hypoglycemia as a model of stress was not followed by hypersecretion of adrenal androgens and revealed no signs of steroid enzyme disturbances in women with PCOS.

Mifepristone modulation of ACTH and CRH regulation of bovine adrenocorticosteroidogenesis in vitro

Mifepristone (RU486), bovine corticotropin-releasing hormone (CRH), arginine vasopressin (VP), adrenocorticotropin (ACTH1-24), and protein kinase activators (forskolin, [FSK]; phorbol 12-myristate 13-acetate [PMA]) were used in vitro to investigate their direct effect on adrenocorticosteroidogenesis. Bovine adrenocortical fasciculata/reticularis cells (2 x 10(5) viable cells/well) were cultured for 3 d in medium supplemented with 10% fetal calf serum. After incubation for an additional 24 hr in serum-free medium, cells were treated with serum-free medium alone (Control) or various concentrations of ACTH, CRH, VP, FSK, PMA, RU486, and/or various concentrations for 1, 2, 4, or 24 hr. Medium content of cortisol and progesterone were determined by radioimmunoassays. ACTH, CRH, FSK, and PMA each stimulated (P < 0.05) secretion of cortisol in time- and dose-related manners. Although these agents stimulated (P < 0.05) secretion of progesterone in a dose-related manner, medium content of progesterone declined (P < 0.05) over time. The minimal effective doses of ACTH and CRH required to stimulate (P < 0.05) secretion of cortisol relative to the Control over a 4-hr culture period were 0.01 nM and 3 nM, respectively. Relative to observations at 1 hr posttreatment, 24-hr treatment with ACTH or CRH increased the medium content of cortisol by an additional 19.8- and 48-fold, respectively (whereas content of progesterone declined over that time period). VP-stimulated secretion of cortisol was time- (P < 0.05) but not dose-related. Specifically, by 24-hr posttreatment, the medium content of cortisol was increased (P < 0.05) 4.6-fold relative to the quantity of cortisol secreted by 1-hr postaddition of VP (0.01 to 1 microM). Co-treatment with RU486 (1 microM) decreased (p < 0.05) FSK-, ACTH- and CRH-stimulated secretion of cortisol by 77, 27, and 56%, respectively. Similarly, the stimulatory effects of ACTH and CRH on progesterone secretion were reduced (P < 0.05) by 40 and 22%, respectively, by co-addition of RU486. The inhibitory action of RU486 on production of cortisol was no longer apparent by 24 hr after treatment. These observations indicate that RU486 can act as a steroid agonist and as well as an antagonist. These data characterize time- and dose-related direct actions of ACTH, CRH, and RU486 on adrenocorticosteroidogenesis. This information will assist efforts to clarify complex intra-adrenal interactions of neurohormones, growth factors, and endogenous steroids.

Dual regulation of 21-hydroxylase activity by sex steroid hormones in rat hepatocytes

In the rat liver, cytochrome P450 catalyzes the hydroxylation of steroid hormones. The expression and activity of some P450 isozymes are regulated by sex steroid hormones. Steroid 21-hydroxylase activity in rat liver is provided mainly by CYP2C6. We studied the regulation of 21-hydroxylase activity by sex steroid hormones in rat primary hepatocyte culture. We added estrogens (estrone, estradiol, estriol) and androgens (testosterone, dihydrotestosterone), (ranging from 10(-9) to 10(-5)M) to the culture. The 21-hydroxylase activity was stimulated by estrogens and was suppressed slightly by androgen in a dose-related manner. The results of our studies demonstrated that sex steroid hormones act differently on 21-hydroxylase activity in rat hepatocytes and, thus, support the hypothesis that the extra-adrenal production of deoxycorticosterone from circulating progesterone is increased during pregnancy by the massive presence of estrogens.

Regulation of adrenocorticotropin secretion in vitro by anterior pituitary corticotrophs from fallow deer (Dama dama)

The actions of corticotropin-releasing hormone (CRH), vasopressin (VP), the synthetic glucocorticoid dexamethasone (DEX), and mifepristone (RU 486), a glucocorticoid antagonist, on the secretion of adrenocorticotropin (ACTH) by cultured fallow deer corticotrophs were studied in vitro. On Day 5 of primary culture, corticotrophs were challenged for up to 4 hr with medium alone (Control), CRH, VP, DEX, forskolin (FSK), phorbol ester (TPA), cyclic AMP (cAMP), and/or RU 486 at various concentrations and combinations. CRH, VP, FSK and TPA each stimulated (P < 0.01) the secretion of ACTH in dose- and time-related manners. Relative to Control, CRH at 0.001 and 0.1 microM and VP at 0.01 and 1 microM increased (P < 0.01) medium concentration of ACTH by 7.3-, 13.5-, 3.7- and 9.0-fold, respectively. There was a treatment x incubation time interaction (P < 0.01) such that at 30-min posttreatment, CRH-induced ACTH secretion tended (P < 0.10) to be less than that obtained via VP treatment, whereas at 1, 3, and 4 hr posttreatment, medium concentration of ACTH from cells treated with 0.1 microM CRH was greater (P < 0.05) than that in cells treated with 1 microM VP. At equimolar doses of 0.01 and 0.1 microM, CRH was 3.4- and 3.0-fold more potent (treatment x dose, P < 0.05) than VP. Cotreatment with 1 microM DEX reduced (P < 0.001) the stimulatory effects of CRH (0.1 microM), VP (1 microM), FSK (10 microMs), TPA (0.1 microM), and cAMP (0.001 M). However, the coaddition of RU 486 (1 microM) to the CRH plus DEX- and the FSK plus DEX-treated wells partially negated the inhibitory effects of DEX. RU 486 completely negated the inhibitory effects of DEX on the VP-, TPA-, and cAMP-stimulated secretion of ACTH. These data indicate that CRH is a more potent stimulator of ACTH secretion than is VP in primary culture of fallow deer pituitary cells. This study also demonstrates the utility of an in vitro culture system to investigate stress-related hormonal interactions in cervids.

Steroidogenesis in guinea pig adrenal cortex: effects of ACTH on steroid secretion and steroidogenic enzyme activities and expression

In this study, we investigated guinea pig adrenal steroidogenesis, specially, C19 steroid production. Analysis of adrenal steroids by high performance liquid chromatography and gas chromatography indicated the presence of androstenedione and 11β-hydroxyandrostenedione. Adrenal androstenedione and 11β-hydroxyandrostenedione levels were stimulated by ACTH administration while only 11β-hydroxyandrostenedione was increased in plasma. In vitro studies using adrenal cortex cells in primary culture confirmed that 11β-hydroxyandrostenedione is the major C19 steroid secreted. The chronic treatment of guinea pig with ACTH stimulated all adrenal post-pregnenolone enzyme activities and decreased P 450c17 mRNA levels while P 450scc, 3β-hydroxysteroid dehydrogenase and P450c11 mRNAs remained unaffected. Treatment of adrenal cells in primary culture with ACTH for 72 h changed the distribution of steroids secreted and decreased 21-hydroxylase activity while 17α-hydroxylase and 17,20-lyase activities were increased favoring C19 steroid production. In ACTH-treated cells, the mRNA levels for P450c21 and P450c17 increased and reached a peak at 18 h. Our data indicate that treatment with ACTH stimulates adrenal steroidogenic capacity by increasing steroid secretion and causes transcriptional and post-transcriptional effects on steroidogenic enzymes gene expression. Finally, the direct action of steroids on steroid production by adrenal cells in primary culture was investigated. Our data indicate that steroids themselves increase C19 steroid synthesis and inhibit glucocorticoid production without affecting gene expression for steroidogenic enzymes.

Studies of adrenal steroidogenic enzymes in guinea pigs

In the present study we found that 3 beta-hydroxysteroid dehydrogenase 4-ene-5-ene-isomerase (3 beta-HSD), 17-hydroxylase and 17,20-lyase (P-450c17), and 21-hydroxylase (P-450c21) activities in a suspension of cells from guinea pig zona reticularis (RE) were 10- to 15-fold less than those measured in cells from zona fasciculata-glomerulosa (FG). Whereas the secretion of cortisol and C-19 steroids was remarkably increased during treatment of FG cells with adrenocorticotropic hormone (ACTH), no response could be detected when using cells from zona RE. By contrast, the measurement of a series of C-21 and C-19 steroids shows that the concentrations of several steroids were greater in the zona RE than in the zona FG. In addition, using Northern blot analysis, we have observed that the basal steady-state levels of mRNA for cholesterol side-chain cleavage (P-450scc), 3 beta-HSD, P-450c21, P-450c17, and P-450c11 were in the same range in the two zones and an administration of ACTH caused, in both zona FG and zona RE, a two- to threefold decrease in P-450c17 and P-450c21 steady-state mRNA levels, whereas P-450c11, 3 beta-HSD, and P-450scc steady-state mRNA levels remained unchanged. Our data suggest the presence of some factor(s) capable of rapidly deactivating the steroidogenic enzymes in the zona RE.

Steroid and xenobiotic effects on the adrenal cortex: mediation by oxidative and other mechanisms

Because steroids reach high concentrations within the adrenal cortex, effects of the direct interaction of steroids and cytochrome P450 enzymes are possible and may involve oxidative damage. Steroid pseudosubstrate effects studied in cultured adrenocortical cells show that these effects are probably not mediated by steroid receptors. Release of oxidants during pseudosubstrate interaction with cytochrome P450s may be responsible for loss of enzymatic activity observed; enzyme activity can be protected by cytochrome P450 inhibitors, antioxidants, and lowered oxygen concentration. There may be pathological effects of pseudosubstrates in the adrenal cortex. Cytochrome P450/pseudosubstrate effects could be involved in the aging and death of adrenocortical cells in vivo, and necrosis of the adrenal cortex due to excessive ACTH stimulation or due to the action of adrenolytic chemicals could result from damage by oxygen radicals originating from cytochrome P450s. The possible mechanism of damage to the adrenal cortex by the xenobiotics dimethylbenzanthracene, TCDD, 3-methylcholanthrene, and o', p'-DDD are reviewed.

Regulation of steroid 17 alpha-hydroxylase in adrenocortical cells in culture

The regulation of steroid 17 alpha-hydroxylase in human and bovine adrenocortical cells in culture is reviewed. It is shown that (i) the long-term growth and cloning of normal human fetal adrenocortical cells in culture is feasible; (ii) the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA) is an effective mitogen in both clonal cultures and non-clonal early cultures of human adrenocortical cells, and shows a selective action in promoting adrenocortical cell growth and inhibiting fibroblast growth; (iii) the key steroidogenic enzymes, 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), are under dual regulation by the cyclic AMP and protein kinase C second messenger systems; (iv) for 17 alpha-hydroxylase, this dual regulation is mediated by changes in 17 alpha-hydroxylase mRNA levels; (v) bovine adrenocortical cells can be transfected with SV40 T antigen, producing lines with elevated differentiated functions, including stabilized high expression of 17 alpha-hydroxylase; (vi) human adrenocortical cells can also be transfected with SV40 large T antigen, giving rise to functional cell lines which may be useful in future studies of 17 alpha-hydroxylase regulation.