Danazol inhibits human adrenal 21-and 11 beta-hydroxylation in vitro

Drug-induced endocrine blood pressure elevation

Patients with uncontrolled hypertension are at risk for cardiovascular complications. The majority of them suffers from unidentified forms of hypertension and a fraction has so-called secondary hypertension with an identifiable cause. The patient's medications, its use of certain herbal supplements and over-the-counter agents represent potential causal factors for secondary hypertension that are often overlooked. The current review focuses on drugs that are likely to elevate blood pressure by affecting the human endocrine system at the level of steroid synthesis or metabolism, mineralocorticoid receptor activity, or by affecting the catecholaminergic system. Drugs with known adverse effects but where benefits outweigh their risks, drug candidates and market withdrawals are reviewed. Finally, potential therapeutic strategies are discussed.

A benefit-risk assessment of medical treatment for uterine leiomyomas

The growth of a uterine leiomyoma growth stops and regresses after the menopause suggesting that leiomyoma growth is dependent on ovarian steroids. Therefore, estrogen has received much attention as the major factor responsible for the development of uterine leiomyomas, but progesterone also plays an important role in development of this disease. Cytogenetic analyses of resected samples has revealed that about 40 to 50% of leiomyomas show karyotypically detectable chromosomal abnormalities. Gonadotrophin releasing hormone (GnRH) agonists exert their action through the suppression of endogenous gonadotrophins and gonadal steroid secretion. Significant reductions of uterine/leiomyoma volume under GnRH agonist therapy has been reported in several studies. However, the leiomyoma generally returns to its pretreatment volume within a few months after discontinuation of the GnRH agonist. To minimise the adverse effects of hypoestrogenism during GnRH agonist treatment, add back therapy can be used (estrogen-progestin, progestin alone and recently tibolone). Antiprogestins have a potential clinical utility in uterine leiomyomas. Mifepristone is a synthetic steroid with both antiprogesterone and antiglucocorticoid activities, that may have an inhibitory effect on growth of leiomyoma. Danazol is an isoxazole of 17beta-ethinyl testosterone, a synthetic steroid, which has a suppressive effect on sex hormone binding globulin concentrations, resulting in efficacy in the short-term treatment of uterine leiomyomas. Gestrinone is a tri-enic steroid with antiestrogen and antiprogesterone properties and has been shown to reduce uterine volume and stop bleeding. Growth factors play a relevant role on the pathophysiology of uterine leiomyoma and probably the inhibition of the action of growth factors on the myometrium will be the basis for future therapy. A number of agents are under investigation for treating uterine leiomyoma. Agents developed from increasing genetic knowledge of this condition could represent, in the next few years, new trends in the medical treatment of uterine leiomyomas.

Steroidogenesis in human adrenocortical carcinoma: biochemical activities, immunohistochemistry, and in situ hybridization of steroidogenic enzymes and histopathologic study in nine cases

To obtain a better understanding of steroid metabolism associated with adrenocortical malignancy we studied steroidogenesis in nine cases of adrenocortical carcinoma (six with Cushing's syndrome, two without clinically significant adrenocortical hormonal abnormalities, and one with primary aldosteronism) by analyzing biochemical enzyme activities (21-hydroxylase and 11 beta-hydroxylase) and by immunohistochemistry and in situ hybridization of steroidogenic enzymes in carcinoma tissues. 21-Hydroxylase activity was markedly low but 11 beta-hydroxylase activity was only moderately decreased compared with normal adrenal activity. Immunohistochemical study of steroidogenic enzymes revealed that six of the nine cases expressed all the enzymes required for cortisol or aldosterone biosynthesis. Immunoreactivity of these enzymes was predominantly observed in small carcinoma cells with compact and/or clear cytoplasm and minimum morphologic nuclear atypia. In those cases with positive steroidogenic enzymes immunohistochemical examination of serial tissue sections revealed that a number of carcinoma cells did not express all the enzymes required for the synthesis of biologically active steroids. This may account for an increased level of precursor steroid secretion associated with adrenocortical malignancy. In situ hybridization of cytochrome 17 alpha-hydroxylase demonstrated that carcinoma cells with positive hybridization signals generally were positive for immunoreactivity, but a discrepancy between mRNA and protein expression was occasionally observed. Although the conclusions derived from our current study are limited by the small number of cases, ineffective corticosteroidogenesis, characteristic of steroid metabolism in human adrenocortical carcinoma, was considered to be due to disorganized expression of steroidogenic enzymes in individual carcinoma cells.

Comparison of the pharmacology of nafarelin and danazol

The pharmacologic profiles of danazol and nafarelin differ considerably from each other. Danazol interacts with multiple classes of proteins, whereas the gonadotropin-releasing hormone agonist nafarelin interacts only with the pituitary gonadotropin-releasing hormone receptor. Differences in the molecular, endocrine, and clinical pharmacologic properties of these agents may provide clues to their varying effects in the management of women with endometriosis.

The effects of nicotine, cotinine and anabasine on rat adrenal 11 beta-hydroxylase and 21-hydroxylase

The effects of nicotine, cotinine and anabasine on rat adrenal steroidogenesis were examined by spectral and enzymatic techniques. The addition of nicotine, cotinine or anabasine to preparations of rat adrenal mitochondria produced type II cytochrome P-450 difference spectra. The addition of nicotine or anabasine, but not cotinine, to rat adrenal microsomes yielded type II cytochrome P-450 difference spectra. Nicotine and anabasine competitively inhibited rat adrenal mitochondrial 11 beta-hydroxylase and microsomal 21-hydroxylase. Cotinine competitively inhibited mitochondrial 11 beta-hydroxylase, but did not inhibit microsomal 21-hydroxylase. The apparent enzymatic inhibition constants for cotinine, nicotine, anabasine and metyrapone inhibition of the mitochondrial 11 beta-hydroxylase were 32, 96, 120 and 74 microM respectively. These studies suggest that components of cigarette smoke may alter patterns of adrenal steroidogenesis.

Effects of danazol on steroidogenesis and gonadotropic responsiveness in isolated human preovulatory follicular cells

In order to investigate the influence of danazol on steroidogenesis and gonadotropic responsiveness of human follicular cells, granulosa and thecal cells of preovulatory follicles were isolated and separately incubated for short term periods. Human chorionic gonadotropin (hCG) (100 IU/ml), FSH (0.5 IU/ml) and danazol (10 micrograms/ml) alone or in combination were added to the incubation medium. Following incubation the cellular cyclic adenosine 3'5' monophosphate (cAMP) levels and the medium content of progesterone (P), androstenedione (A) and 17 beta-estradiol (E2) were determined. All follicles included in the study were classified as nonatretic and well developed, i.e. less than 3 days before ovulation. Human chorionic gonadotropin caused an increase in cAMP formation in both cell-types and this effect was significantly counteracted by danazol in vitro. In granulosa cells danazol tended to counteract a stimulatory effect of FSH on cAMP formation. No significant influence of danazol was found on the basal steroid formation of both cell types during short term incubation. On the other hand, danazol significantly counteracted the FSH stimulated P formation of the granulosa cells and the hCG stimulated A and E2 formation of the thecal cells. It is concluded that danazol inhibits gonadotropin-stimulated steroidogenesis locally in the human follicular cells and that this effect of danazol is mediated via the cyclic AMP system.

Inhibition of gonadotropin-releasing hormone receptors in rat anterior pituitary monolayer cell cultures by danazol

To study possible cellular antigonadotropic effects of danazol, monolayer cultures of anterior pituitary cells from immature female rats were treated with danazol. Measurements of luteinizing hormone release in response to 10(-8) mol/L gonadotropin-releasing hormone challenge and iodine 125-labeled gonadotropin-releasing hormone binding activity were done after exposure to increasing concentrations of danazol and for increasing lengths of time. It was found that luteinizing hormone secreted by pituitary cells in response to gonadotropin-releasing hormone was inhibited after danazol treatment in a dose- and time-dependent manner when compared to controls. Also, a 45% decrease in gonadotropin-releasing hormone receptor binding capacity was observed in pituitary cells cultured in the presence of increasing concentrations of danazol in the range of 10(-8) to 10(-4) mol/L when compared to controls. Furthermore, exposure to danazol for 25 to 96 hours caused a marked decrease in gonadotropin-releasing hormone binding activity (p less than 0.005). Under these experimental conditions danazol treatment decreased the pituitary receptors for gonadotropin-releasing hormone in a dose- and time-dependent manner. Scatchard analysis of saturation curves for the binding of gonadotropin-releasing hormone to cellular gonadotropin-releasing hormone receptors indicated that the observed decrease in gonadotropin-releasing hormone binding in the danazol-treated group was due to a change in the number of gonadotropin-releasing hormone binding sites rather than a change in the affinity. It is therefore concluded that the antigonadotropic activity of danazol appears to be related to a decrease in gonadotropin-releasing hormone receptors in the pituitary.

Some characteristics of human adrenal microsomal 21-hydroxylase activity

The following general characteristics of 21-hydroxylase activity were determined using pooled microsomes obtained from three glands. Enzyme activity exhibited a broad pH dependence, being optimal between pH 7.4-pH 7.8, and was maximal with NADPH in the range 2 to 4.75 X 10(-4)mol/l. No microsomal 21-hydroxylase activity was detected in the absence of NADPH or substrate and when heat denatured microsomes were employed. Enzyme activity was depressed by greater than 75% in the presence of 100% oxygen or nitrogen. In a second set of experiments, microsomal fractions were prepared individually from 7 glands. In the presence of 17 alpha-hydroxy progesterone (2.0 X 10(-7) and 2.0 X 10(-6)mol/l) product formation was linear with time for up to 90 s when the microsomal protein concentration was 5, 10 and 20 micrograms/ml. Between 5 and 30% of the substrate was converted during the first 60 s. In 5/7 of the glands the addition of the autologous cytosol (20 micrograms protein/ml) was without effect, and enzyme activity (using a 60 s reaction and either 2.0 X 10(-7) or 2 X 10(-6)mol/l 17 alpha-hydroxy progesterone was directly proportional to the microsomal protein concentration (range 0-20 micrograms/ml). With the other 2 adrenals 21-hydroxylation was not proportional to the same range of microsomal protein concentrations, although it became so upon the addition of cytosol, which significantly augmented activity. There was considerable variation in enzyme activity between glands from different individuals (Vmax ranging from 2.6 to 16.6 X 10(-9) mol/min/mg protein) and in the apparent Km's (from 0.22 to 1.1 X 10(-6)mol/l). In the two preparations sensitive to cytosol, the Vmax increased 2-fold, and the Km was 3 times lower. Cytosol was without effect upon the kinetic characteristics of the other 5 microsomal preparations. Ascorbic acid (1 X 10(-3) mol/l) depressed enzyme activity by 25-43% whereas oxidised and reduced glutathione (1 X 10(-3) mol/l) showed a slight and variable effect upon 21-hydroxylation.

Actions of danazol in vivo on cytochrome P-450 and steroidogenic enzymes in rat testis and liver microsomal preparations

The mechanism of action of danazol has not been established and the drug may act at multiple loci. Effects suggesting inhibition of pituitary gonadotropin release have been described while some in vitro studies have demonstrated competitive inhibition of steroidogenic enzymes. In addition, destruction of cytochrome P-450 by the acetylenic moiety of danazol is a possible mechanism. Following 14 days of danazol treatment (10 mg/kg/day), the specific content of rat testis microsomal cytochrome P-450 and the serum testosterone were decreased, in spite of no significant change in serum luteinizing hormone. Furthermore, simultaneous administration of human chorionic gonadotropin with danazol still resulted in a decrease in cytochrome. The activities of two testicular microsomal steroid-converting enzymes (17 alpha-hydroxylase and 17,20-lyase) were not altered when based on cytochrome P-450 content but were markedly depressed when based on microsomal protein. In liver, danazol showed a similar but less marked dimunition of the cytochrome. Surprisingly, steroid 17 alpha-hydroxylase activity in liver was significantly increased while other cytochrome P-450 dependent enzyme activities were not altered.

Danazol: endocrine pharmacology and therapeutic applications

The options for the medical management of endometriosis have been expanded by the introduction of the synthetic steroid, danazol. The results of large clinical studies suggest that danazol treatment produces significant improvement in the symptoms, signs, and laparoscopic findings of endometriosis. The original studies of the pharmacology of danazol concluded that danazol was a strong antigonadotrophin with mild androgenic effects and no other hormonal properties. Recent studies which emphasize the molecular pharmacology of danazol suggest that this steroid has direct effects on hypothalamic-pituitary function, multiple classes of steroid receptors, gonadal steroidogenesis, and endogenous steroid metabolism. These studies demonstrate that: (1) danazol prevents the midcycle surge of luteinizing hormone (LH) and follicle-stimulating hormone (FSH); (2) danazol does not significantly suppress basal LH or FSH in gonadally intact human beings; (3) in castrated animals danazol can prevent the compensatory increase in LH and FSH; (4) danazol binds to androgen, progesterone, and glucocorticoid receptors; (5) danazol does not bind to estrogen receptors; (6) danazol binds to sex hormone-binding globulin and corticosteroid-binding globulin; (7) danazol inhibits multiple enzymes of steroidogenesis; (8) danazol increases the metabolic clearance rate of progesterone; and (9) metabolites of danazol are hormonally active. Given the complex pharmacology of danazol it is inappropriate to continue to refer to danazol as a "selective antigonadotrophin."U