Expression of adrenal cytochromes P-450 in testosterone-induced hypertension

Changes in plasma aldosterone and electrolytes levels, kidney epithelial sodium channel (ENaC) and blood pressure in normotensive WKY and hypertensive SHR rats following gonadectomy and chronic testosterone treatment

We hypothesized that testosterone-induced increase in blood pressure involve changes in aldosterone levels and expression of epithelial sodium channel (ENaC) in the kidneys.

METHODS

Ovariectomized female normotensive Wistar Kyoto (WKY) and Spontaneous hypertensive (SHR) rats were given six weeks treatment with testosterone via subcutaneous silastic implant. The rats were anesthetized and mean arterial pressure (MAP) was measured via direct cannulation of the carotid artery. Animals were sacrificed and kidneys were removed and subjected for α, β and γ-ENaC protein and mRNA expression analyses by Western blotting and Real-time polymerase chain reaction (qPCR), respectively. Distributions of α, β and γ-ENaC proteins in kidneys were observed by immunofluorescence. Plasma testosterone, aldosterone, electrolytes, osmolality, urea and creatinine levels were determined by biochemical assays. Analysis were also performed in non-testosterone treated orchidectomized and sham-operated male WKY and SHR rats.

RESULTS

Treatment of ovariectomized female WKY and SHR rats with testosterone causes increased in MAP but decreased in plasma aldosterone, sodium (Na⁺), osmolality and expression and distribution of α, β and γ-ENaC subunits in the kidneys. Orchidectomy decreased the MAP but increased plasma aldosterone, Na⁺, osmolality and α, β and γ-ENaC expression and distribution in the kidneys of male WKY and SHR rats.

CONCLUSIONS

Decreased in plasma aldosterone, Na⁺ and ENaC levels in kidneys under testosterone influence indicated that testosterone-induced increased in MAP were not due to increased plasma aldosterone and ENaC levels in kidneys, and thus the testosterone effect on MAP likely involve other mechanisms.

Fetal origin of endocrine dysfunction in the adult: the phthalate model

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer with endocrine disrupting properties that is found ubiquitously in the environment as well as in human amniotic fluid, umbilical cord blood, human milk, semen, and saliva. It is used in the industry to add flexibility to polyvinyl chloride-derived plastics and its wide spread use and presence has resulted in constant human exposure through fetal development and postnatal life. Epidemiological studies have suggested an association between phthalate exposures and human reproductive effects in infant and adult populations. The effects of fetal exposure to phthalates on the male reproductive system were unequivocally shown on animal models, principally rodents, in which short term deleterious reproductive effects are well established. By contrast, information on the long term effects of DEHP in utero exposure on gonadal function are scarce, while its potential effects on other organs are just starting to emerge. The present review focuses on these novel findings, which suggest that DEHP exerts more complex and broader disruptive effects on the endocrine system and metabolism than previously thought. This article is part of a Special Issue entitled "CSR 2013".

Flutamide increases aldosterone levels in gonadectomized male but not female Wistar rats

BACKGROUND

Sex-specific differences in blood pressure (BP) suggest an important modulating role of testosterone in the kidney. However, little is known about the interaction between androgens and the mineralocorticoid aldosterone. Our objective was to determine the effects of testosterone in gonadectomized male and female rats on a low-salt diet, and to determine the effect of androgen receptor (AR) blockade by flutamide on BP and on aldosterone levels.

METHODS

Normotensive male and female Wistar rats were gonadectomized and put on a low-salt diet. They were treated for 16 days with testosterone or placebo. In addition, the animals received the AR antagonist flutamide or placebo, respectively. BP was measured by tail-cuff method, 24-h urine samples were collected in metabolic cages and blood was collected for hormonal measurements.

RESULTS

Testosterone increased BP in males and females, and this effect could be blocked by flutamide. Flutamide treatment itself significantly increased aldosterone levels in male but not in female rats. These elevated aldosterone levels could be lowered by testosterone treatment during AR blockade. Accordingly to aldosterone levels, flutamide increased in males the serum sodium/potassium to urinary sodium/potassium ratio, an in vivo indicator of renal aldosterone action.

CONCLUSIONS

Testosterone regulates BP in male and female gonadectomized rats via the AR. Flutamide by itself exerts influence over aldosterone in the absence of gonadal steroid replacement suggesting AR involvement in renal sodium handling. These flutamide effects were sex-specific and not seen in female rats.

Cardiovascular disease and androgens: a review

Globally, cardiovascular disease is the single largest cause of mortality. The differences in pattern of cardiovascular disease between the two genders have not been explained properly. The spotlight has largely been focused on estrogens but no conclusive evidence has proven its role in reducing the incidence of cardiovascular disease. Consequently, androgens have attracted significant interest in explaining the gender difference in cardiovascular disease. More studies in last two decades have increased our knowledge about the effects of androgens on cardiovascular disease progression. Evidence for age related fall in testosterone levels in males and increasing cardiovascular events with age had lead to the postulation of idea of 'andropause or male menopause'. Unfortunately, for the last few decades the androgens have been highlighted as agents of abuse among athletes all over the world. There have been multiple reports of their association with sudden cardiac death and adverse cardiovascular outcomes when abused. Contrastingly, there has been an increasing prescription use of testosterone supplementation in various conditions related to androgen deficiency state and for many other off-label indications. Human observational studies have mostly concluded that men with lower testosterone levels tend to have higher incidence of coronary artery disease. Emerging evidence supports that lower androgen levels predict poor cardiovascular risk profile. Role with supplementation of testosterone for cardiovascular disease is being studied in both primary and secondary prevention stages and its safety being evaluated. This is an appropriate time to review the role of androgens specifically from a cardiovascular standpoint.

Impact of nandrolone decanoate on gene expression in endocrine systems related to the adverse effects of anabolic androgenic steroids

Elite athletes, body builders and adolescents misuse anabolic-androgenic steroids (AAS) in order to increase muscle mass or to enhance physical endurance and braveness. The high doses misused are associated with numerous adverse effects. The purpose of this study was to evaluate the impact of chronic supratherapeutic AAS treatment on circulating hormones and gene expression in peripheral tissues related to such adverse effects. Quantitative real-time PCR was used to measure expression levels of in total 37 genes (including peptide hormones, cell membrane receptors, nuclear receptors, steroid synthesising enzymes and other enzymes) in the pituitary, testes, adrenals, adipose tissue, kidneys and liver of male Sprague-Dawley rats after 14-day administration of the AAS nandrolone decanoate, 3 or 15 mg/kg. Plasma glucose and levels of adrenocorticotropic hormone (ACTH), adiponectin, corticosterone, ghrelin, insulin and leptin were also measured. We found several expected effects on the hypothalamic-pituitary-gonadal axis, while the treatment also caused a number of other not previously identified changes in circulating factors and gene transcription levels such as the dose-dependent reduction of the beta(3)-adrenergic receptor in adipose tissue, reduction of both circulating and mRNA levels of adiponectin, up-regulation of both hydroxymethylglutaryl-CoA-reductase, the rate-limiting enzyme in de novo synthesis of cholesterol, and the receptor for ACTH in the adrenals. The results provide evidence for wide ranging effects of AAS on the hypothalamic-pituitary-adrenal axis, adipose tissue and substrates of the renal control of blood pressure.

Medroxyprogesterone acetate but not drospirenone ablates the protective function of 17 beta-estradiol in aldosterone salt-treated rats

Controversial results obtained from human and animal studies on the prevention of heart disease by estrogens and progestins warrant a better understanding of nuclear hormone receptor function and interaction. To address this issue and taking into account that effects of synthetic progestins are not only referable to action through the progesterone receptor but may also be mediated by other steroid receptors, we characterized cardiovascular function and inflammatory gene expression in aldosterone salt-treated rats on long-term administration of 17beta-estradiol, medroxyprogesterone acetate, and drospirenone, a new progestogen exhibiting antimineralocorticoid activity. The complex pattern of cardiovascular injury in ovariectomized Wistar rats induced by chronic aldosterone infusion plus a high-salt diet was significantly attenuated in sham-ovariectomized rats and by coadministration of 17beta-estradiol in ovariectomized animals after 8 weeks of continuous treatment. The beneficial role of 17beta-estradiol on blood pressure, cardiac hypertrophy, vascular osteopontin expression, perivascular fibrosis, and impaired NO-dependent relaxation of isolated aortic rings was completely abrogated by coadministration of medroxyprogesterone acetate. In contrast, drospirenone was either neutral or additive to 17beta-estradiol in protecting against aldosterone salt-induced cardiovascular injury and inflammation. The current results support the hypothesis of complex interactions among estrogen, progesterone, glucocorticoid, androgen, and mineralocorticoid receptor signaling in cardiovascular injury and inflammation. Novel progestins, such as drospirenone, confer superior effects compared with medroxyprogesterone acetate in a model of aldosterone-induced heart disease because of its antimineralocorticoid properties.

Inhibition of aldosterone production by testosterone in male rats

In vivo and in vitro experiments were designed to assess the effect of testosterone on aldosterone secretion in male rats. Orchidectomized rats were injected subcutaneously with oil or testosterone propionate ([TP] 2 mg/kg) for 7 days. Intact rats were injected with oil only. The results indicate that the plasma aldosterone level was higher in orchidectomized versus intact and TP-replaced rats. In the in vitro study, testosterone caused a marked decrease of aldosterone secretion by zona glomerulosa (ZG) cells, but failed to alter the accumulation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP). Testosterone significantly decreased the corticotropin (ACTH)-stimulated production of aldosterone and accumulation of cAMP in rat ZG cells. The conversion of corticosterone to aldosterone and of 25-OH-cholesterol to pregnenolone, as well as angiotensin II (ANG II)-stimulated production of aldosterone, were decreased by testosterone. These results suggest that testosterone inhibits the basal and ANG II- and ACTH-stimulated release of aldosterone, via inhibition of aldosterone synthase activity and cytochrome P-450 side-chain cleavage (P450scc) activity, and ACTH-stimulated cAMP accumulation in rat ZG cells.

The cardiac toxicity of anabolic steroids

Anabolic steroids are synthetic derivatives of testosterone that were developed as adjunct therapy for a variety of medical conditions. Today they are most commonly used to enhance athletic performance and muscular development. Both illicit and medically indicated anabolic steroid use have been temporally associated with many subsequent defects within each of the body systems. Testosterone is the preferred ligand of the human androgen receptor in the myocardium and directly modulates transcription, translation, and enzyme function. Consequent alterations of cellular pathology and organ physiology are similar to those seen with heart failure and cardiomyopathy. Hypertension, ventricular remodeling, myocardial ischemia, and sudden cardiac death have each been temporally and causally associated with anabolic steroid use in humans. These effects persist long after use has been discontinued and have significant impact on subsequent morbidity and mortality. The mechanisms of cardiac disease as a result of anabolic steroid use are discussed in this review.

Cytochrome c oxidase in rat adrenal and liver: effects of anti-androgen treatment and studies in testicular feminized rats

The role of androgen receptors in androgen-induced changes in rat adrenocortical and liver cytochrome c oxidase (COX) has been investigated. The anti-androgen flutamide, blunted the increase in COX activity and COX subunits II/III and IV, that is seen with androgen treatment. Testicular feminized (Tfm) rats had levels of COX activity and COX subunits II/II and IV in adrenal cortex and liver that were intermediate between the high levels found in normal male rats and the lower levels of normal female rats. These data suggest that androgen effects on adrenal and liver COX are mediated through interactions with androgen receptors known to be present in these issues. However, the observed changes in COX activity and COX subunits were not accompanied by altered levels of mRNAs encoding for COX II or COX IV.

Sex differences in cytochromes oxidase and P-45011 beta in the rat adrenal cortex

A comparative study of cytochrome c oxidase (COX) activity and expression as well as cytochrome P-45011 beta expression has been carried out on the adrenal cortex of male and female rats. COX has also been examined in rat liver. In addition, the effect of testosterone replacement in orchiectomized male rats on adrenal COX has also been investigated. Adult male rats had higher COX activity in adrenal (255%) and liver (144%) mitochondria compared to adult female rats. Male rat adrenals and liver also had increased levels of COX II, a mitochondria-encoded COX subunit, and of COX IV, a nucleus-encoded COX subunit, as measured by Western analysis. In contrast, cytochrome P-45011 beta levels were lower (48%) in adrenal mitochondria from male rats than those of female rats. There was no significant sex difference in the level COX II and COX IV mRNAs in adrenal or liver, whereas the cytochrome P-45011 beta mRNA was 4-fold higher in female adrenals than in males. In male rats, orchiectomy caused a 23% decrease and testosterone replacement a 66% increase in adrenal COX activity. There were no corresponding changes in the levels of mRNAs encoding for COX subunits, suggesting post-transcriptional effects of testosterone on COX. These results are consistent with a regulatory role of testosterone on the expression of components of the respiratory and steroidogenic electron transport chains.

Influence of androgen on tyrosine hydroxylase mRNA in adrenal medulla of spontaneously hypertensive rats

We investigated the effects of castration and testosterone propionate on tyrosine hydroxylase mRNA, its activity, and catecholamine synthesis in the adrenal medulla of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Four-week-old male rats were castrated. Testosterone propionate (500 micrograms per rat) was administered subcutaneously twice a week to castrated rats (between 14 and 25 weeks of age). Systolic pressure was measured at the age of 25 weeks, and rats were decapitated. The systolic pressure of castrated SHR was significantly lower than that of control and testosterone-replaced SHR. Epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA in the adrenal medulla of castrated SHR were significantly lower than in control and testosterone-replaced SHR. Systolic pressure and epinephrine and norepinephrine levels, tyrosine hydroxylase activity, and tyrosine hydroxylase mRNA levels in the adrenal medulla of WKY showed no significant differences among the control, castrated, and testosterone-replaced groups. These results suggest that androgens contribute to the development and maintenance of hypertension in SHR via sustained enhancement of tyrosine hydroxylase synthesis in the adrenal medulla, leading to increased epinephrine and norepinephrine levels.

Sex differences in the steroidogenic and respiratory electron transport chains in the rat adrenal cortex

Both steroid 11 beta-hydroxylation and cholesterol side chain cleavage occur in the mitochondria of adrenocortical cells and they require reducing power in the form of NADPH. There are direct sources of NADPH in rat adrenal mitochondria but another potential source of NADPH is the energy-linked transhydrogenase reaction. This suggests that there is a relationship between the steroidogenic and respiratory chains. We have elaborated upon this relationship by exploring the expression of cytochrome c oxidase (CO) and cytochrome P-45011 beta. We have studied the regulation of one mitochondrial-encoded (COII) and one nuclear-encoded (COIV) subunit. Normal, untreated male rats had higher basal levels of activity of CO in adrenal (255%) and liver (144%) mitochondria, compared to normal, untreated female rats. They also had increased COII (300% and 138%) and COIV (300% and 135%). Cytochrome P-45011 beta levels, however, were lower (48%) in adrenal mitochondria of male rats than those of female rats. Androgen treatment of male rats caused an increase in the activity of CO in the mitochondria of the adrenal gland with the levels being 171% of the corresponding controls. This increase in activity paralleled an increase in the levels of COII and COIV in the adrenal as measured by Western analysis. In contrast, adrenal cytochrome P-45011 beta levels were lower (68%). Androgen treatment caused no significant change in the levels of mRNA's for COII and COIV whereas cytochrome P-45011 beta mRNA was significantly lower than normal.(ABSTRACT TRUNCATED AT 250 WORDS)