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

Transport of steroid hormones: interaction of 70 drugs with testosterone-binding globulin and corticosteroid-binding globulin in human plasma

This report describes the binding of 70 synthetic compounds to both testosterone-binding globulin (TeBG) and corticosteroid-binding globulin (CBG). The ability of each compound to displace [3H]testosterone from TeBG and [3H]cortisol from CBG adsorbed from a plasma pool onto a solid phase matrix of Concanavalin A-Sepharose was determined under equilibrium conditions at physiological pH and temperature. From these data, the association constants of the compounds for binding to both TeBG and CBG were calculated and used to predict whether endogenous steroid transport would be altered by the therapeutic administration of the drug. Computer simulation predicted that by interacting with TeBG, therapeutic levels of danazol, methyltestosterone, fluoxymesterone, and norgestrel could displace 83%, 48%, 43%, and 16%, respectively, of the concentration of testosterone bound to TeBG in a normal man. Similarly, by interacting with CBG, therapeutic levels of prednisolone could decrease the concentration of cortisol bound to CBG by approximately 32% in both men and women, and despite relatively low affinity binding to TeBG (5 X 10(5) M-1), prednisolone could also displace small amounts of testosterone from TeBG. These results indicate that binding to steroid transport proteins should be considered among the in vivo effects of drugs on endogenous steroid hormone levels.

Transactivation via the human glucocorticoid and mineralocorticoid receptor by therapeutically used steroids in CV-1 cells: a comparison of their glucocorticoid and mineralocorticoid properties

BACKGROUND

Glucocorticoids (GCs) are commonly used for long-term medication in immunosuppressive and anti-inflammatory therapy. However, the data describing gluco- and mineralo-corticoid (MC) properties of widely applied synthetic GCs are often based on diverse clinical observations and on a variety of in vitro tests under various conditions, which makes a quantitative comparison questionable.

METHOD

We compared MC and GC properties of different steroids, often used in clinical practice, in the same in vitro test system (luciferase transactivation assay in CV-1 cells transfected with either hMR or hGRalpha expression vectors) complemented by a system to test the steroid binding affinities at the hMR (protein expression in T7-coupled rabbit reticulocyte lysate).

RESULTS AND CONCLUSIONS

While the potency of a GC is increased by an 11-hydroxy group, both its potency and its selectivity are increased by the Delta1-dehydro-configuration and a hydrophobic residue in position 16 (16-methylene, 16alpha-methyl or 16beta-methyl group). Almost ideal GCs in terms of missing MC effects, as defined by our in vitro assay, are therefore prednylidene, budesonide, beclomethasone and betamethasone.The MC potency of a steroid is increased by a 9alpha- or a 6alpha-fluoro substituent. A hydrophilic substituent in position 16 (like 16-hydroxylation in triamcinolone) decreases both MC and GC properties. As no substituent that leads to an isolated reduction of GC activity could be characterized in our experiments, 9alpha-fluorocortisol, the most frequently used steroid for MC substitution, seems to be the best choice of available steroids for this purpose.

The hypolipidemic natural product guggulsterone acts as an antagonist of the bile acid receptor

Ayurveda, the ancient Indian system of health care and medicine, has a well-organized materia medica in which plants form a dominant part. A key illustration of the exploitation of this knowledge toward the development of a modern drug is the isolation and characterization of two antihyperlipidemic compounds, Z-, and E-guggulsterone from the tree Commiphora mukul, the exudate of which has been traditionally used for mitigating lipid disorders. Here, we demonstrate that Z-guggulsterone and an analog, 80-574 currently in clinical trials, act as antagonists of the bile acid receptor (BAR), a member of the intracellular receptor superfamily. These compounds antagonize the activity of BAR in vitro, and in cell culture systems on promoters and endogenous target genes. In biochemical assays, they are able to displace coactivator peptides from the receptor in a dose-dependent manner. The mechanism by which they act as BAR antagonists is likely through their inability to recruit coactivator proteins, failure to release corepressor proteins from unliganded receptor, and ability to compete with BAR agonists to block coactivator recruitment. Our data suggest these compounds may mediate at least some of their effects via the BAR.

Control of the bovine estrous cycle with melengestrol acetate (MGA): a review

Expanded use of artificial insemination in the beef cattle industry depends on successful application of treatments designed to synchronize estrus. Regulation of estrous cycles is associated with control of the corpus luteum (CL), whose life span and secretory activity are subject to trophic and lytic mechanisms. The advantages of melengestrol acetate (MGA) in estrous synchronization incorporate ease of administration, lower cost relative to other estrous synchronization products, and potential for use to induce estrus in prepubertal heifers. Treatments first designed to synchronize estrous cycles of normally cycling heifers by feeding MGA were imposed daily for 14 to 18 d at levels of .5 to 1 mg. The minimal daily effective dose required to inhibit ovulation was .42 mg. Longer feeding periods of MGA were associated with low fertility at the first synchronized estrus, but at the second estrus, conception was normal. Low fertility at the synchronized estrus resulted in development of alternative treatment practices, which combined feeding of MGA with injections or implants of estradiol-17 beta, estradiol cypionate, luteinizing hormone, human chorionic gonadotropin, pregnant mare serum gonadotropin, or oxytocin. Estrus was synchronized after MGA and estradiol-17 beta or estradiol cypionate treatments, but fertility was low. Short-term feeding of MGA (5 to 7 d) combined with prostaglandin F2 alpha or its analogs (PGF) on the last day of MGA reduced fertility at the synchronized estrus. The reduced conception at first service occurred in animals that began treatment after d 12 of the estrous cycle. However, feeding MGA for 14 d and then injecting PGF 17 d later avoided problems with reduced conception. Fertility of animals after this treatment was similar to that of contemporaries synchronized with Syncro-Mate-B. However, the length of the treatment period creates a need for increased management and may extend management beyond practical limits. Further research is warranted to address problems associated with reduced fertility after short-term treatment with MGA.

Danazol but not gonadotropin-releasing hormone agonists suppresses autoantibodies in endometriosis

The effect of treatment with danazol (n = 10) or gonadotropin-releasing hormone agonists (GnRH-a) (n = 10) on autoantibody (AA) production (IgG, IgM and, IgA to 6 phospholipids, 5 histones, and 4 polynucleotides) in endometriosis was evaluated blindly in a longitudinal, prospective, randomized study. Clinical improvement, ovarian suppression, and resolution of endometriosis were comparable in both groups. Approximately 50% of patients had significant AA abnormalities initially. During treatment with danazol but not GnRH-a, AA gradually decreased in concentration and in number/patient. Total immunoglobulin levels (IgG, IgM, and IgA) also decreased only in the danazol group. This study indicates that danazol, but not GnRH-a, lowers abnormal AA associated with endometriosis.

Danazol increases factor VIII and factor IX in classic hemophilia and Christmas disease

We gave danazol (600 mg per day orally for 14 days), an attenuated androgen, to four adults with classic hemophilia and one adult with Christmas disease. The levels of factor VIII in the patients with classic hemophilia ranged from 1 to 3 per cent before treatment and rose to 3 to 8 per cent during the treatment period. The level of factor IX in the patient with Christmas disease rose from 5 to 14 per cent. The rise in clotting-factor activity was usually observed within five to six days after the initiation of therapy and peaked between 7 and 13 days. The drug had no untoward effects. During the 70 patient-days of therapy, only two patients required plasma products, each on one occasion. These data suggest that danazol therapy may decrease the hemorrhagic tendency and reduce the need for transfusions of plasma products in classic hemophilia and Christmas disease. Controlled clinical trials will be required to establish its value in these applications.

Effects of spironolactone, canrenone and canrenoate-K on cytochrome P450, and 11beta- and 18-hydroxylation in bovine and human adrenal cortical mitochondria

Effects of spironolactone, canrenone and canrenoate-K on adrenal cytochrome P450 (P450) and corticosteroid biosynthesis were examined by studying difference spectra, P450 reduction and corticoid hydroxylation in mitochondrial preparations isolated from zona fasciculata and zona glomerulosa of bovine adrenals and from adrenal adenoma and hyperplastic adrenal cortex removed from patients with hyperaldosteronism. All three agents bound to P450 producing type I difference spectra and underwent hydroxylation. They all inhibited 11beta-hydroxylation in bovine adrenal at 30 muM and higher concentrations. Canrenone, the most potent inhibitor, blocked enzyme activity by 60% at a concentration of 60 muM. Spironolactone stimulated P450 reduction. The order of potency of inhibition was found to correlate with the order of affinity of these agents for P450. 11beta-Hydroxylase in human adrenal appeared to be less sensitive to canrenone. All three agents or their hydroxylated metabolites blocked 18-hydroxylation in bovine adrenal at lower concentrations. Canrenoate-K, being the most effective, inhibited 52% at 20 muM. Low concentrations of canrenone (2.5-5.0 muM) were without effect on 11beta-hydroxylase but markedly inhibited 18-hydroxylation (62-76%) in hyperplastic human adrenals. The inhibitors produced mixed type inhibition of 11beta-hydroxylation and competitive type inhibition of 18-hydroxylation. These findings indicate that at low concentrations spironolactone and its major metabolites, canrenone and canrenoate-K, or their hydroxylated metabolites, can directly interfere with the biosynthesis of aldosterone in bovine and certain human adrenal cortical tissue.

The inhibitory effects of danazol, danazol metabolites, gestrinone, and testosterone on the growth of human endometrial cells in vitro

Danazol and gestrinone are effective drugs in the treatment of endometriosis. Their mechanism of action remains uncertain, but may be related to their androgenic activity. The authors examined the effect of danazol on human endometrial cells cultured in vitro, its two major metabolites, ethisterone and 2 hydroxymethyl ethisterone, gestrinone, and testosterone (T) at 1X and 10X expected plasma concentrations. Danazol and T suppressed growth by 20.8 and 25.0% (P less than 0.01), respectively, at the lower dose, and by 26.9 and 35.5% (P less than 0.01), respectively, at the 10-fold higher dose. No significant suppression of growth occurred with gestrinone, ethisterone, or 2 hydroxymethyl ethisterone. The results provide further evidence that danazol and T (but not gestrinone) may act by a direct effect on endometrial tissue.

Photo-conversion of two epimers (20R and 20S) of pregna-5,7-diene-3beta, 17alpha, 20-triol and their bioactivity in melanoma cells

Pregna-5,7-dienes and their hydroxylated derivatives can be formed in vivo when there is a deficiency in 7-dehydrocholesterol (7-DHC) Delta-reductase function, e.g., Smith-Lemli-Opitz syndrome (SLOS). Ultraviolet B (UVB) radiation induces photoconversion of 7-DHC to vitamin D3, lumisterol3 and tachysterol3. Two epimers (20R and 20S) of pregna-5,7-diene-3beta,17alpha,20-triol (4R and 4S, respectively) were synthesized and their UVB photo-conversion products identified as corresponding 9,10-secosteroids with vitamin D-like and tachysterol-like structures, and 5,7-dienes with inverted configuration at C-9 and C-10 (lumisterol-like). The number and character of the products and the dynamics of the process were dependent on the UVB dose. At high UVB doses, the formation of multiple oxidized derivatives of the primary products, and the formation of 5,7,9(11)-triene, were observed. The production of vitamin D-like, tachysterol-like and lumisterol-like derivatives was also observed in human skin treated with 4R and 4S, and subjected to UV irradiation, as shown by RP-HPLC. Newly synthesized compounds inhibited melanoma growth in dose dependent manner, and some of them showed equal or higher potency than 1,25(OH)2D3. In summary, we have characterized for the first time the products of UV induced conversion of pregna-5,7-diene-3beta,17alpha,20-triols and documented that the newly synthesized compounds have antiproliferative properties against melanoma cells.

The effects of cyproterone acetate and oestradiol upon testosterone stimulated sebaceous activity in the rat

Castrated rats were implanted with testosterone and in addition treated with either cyproterone acetate or oestradiol or both. Testosterone by itself very significantly increased both sebum production and the incidence of sebaceous mitoses. Each of the other compounds significantly reduced sebum production in rats treated with testosterone. Cyproterone acetate reduced the incidence of sebaceous mitoses and the weight of the preputial glands, whereas oestradiol had neither of these effects. When both compounds were given simultaneously, their combined effect in reducing sebaceous secretion was equal to the product of their individual effects. The results reinforce the view that oestrogenic and anti-oestrogenic steroids have different points of action in the sebaceous glands, and suggest that the most effective way of reducing sebaceous activity might be to use both types of compound in combination.

Guggulsterones induce apoptosis and differentiation in acute myeloid leukemia: identification of isomer-specific antileukemic activities of the pregnadienedione structure

In this study, the antileukemic effects of three isomeric pregnadienedione steroids [i.e., cis-guggulsterone, trans-guggulsterone, and 16-dehydroprogesterone] were investigated in HL60 and U937 cells as well as in primary leukemic blasts in culture. Our results show that all three compounds inhibited the proliferation of HL60 and U937 cells, with IC50s ranging from 3.6 to 10.9 micromol/L after treatment for 6 days. These growth inhibitory effects correlated with externalization of phosphatidylserine and loss of mitochondrial membrane potential, suggesting that these isomeric steroids induce apoptosis in leukemia cells. z-VAD-fmk prevented phosphatidylserine externalization but not mitochondrial membrane potential loss, indicating that mitochondrial dysfunction occurred in the absence of caspase activation. Interestingly, although all three compounds increased the generation of reactive oxygen species and decreased phosphorylation of extracellular signal-regulated kinase, only cis-guggulsterone induced a rapid depletion of reduced glutathione levels and oxidation of the mitochondrial phospholipid cardiolipin. 16-Dehydroprogesterone and trans-guggulsterone induced differentiation of HL60 and NB4 cells as evidenced by increased surface expression of CD11b and/or CD14, and all three steroids rapidly induced mitochondrial dysfunction and phosphatidylserine externalization of CD34-positive blasts from primary leukemic samples. This study is the first to show that guggulsterones and 16-dehydroprogesterone exert antileukemic effects via the induction of apoptosis and differentiation and, more importantly, identifies the pregnadienedione structure as a potential chemotherapeutic scaffold.

Spironolactone inhibits production of proinflammatory cytokines by human mononuclear cells

BACKGROUND

The mineralocorticoid receptor antagonist spironolactone (SPIR) reduces the mortality and morbidity in patients with congestive heart failure (CHF). Overexpression of proinflammatory cytokines contribute to the development and progression of CHF.

MATERIAL AND METHODS

We examined the effect of SPIR on in vitro cytokine production by human peripheral blood mononuclear cells (PBMC). PBMC were cultured with 10-1000 microM SPIR and stimulated with lipopolysaccharide or phytohaemagglutinin-P. Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-1beta, and interferon (IFN)-gamma were measured in culture supernatants by enzyme-linked immunosorbent assay and mRNA expression of the cytokines was determined by real-time reverse transcriptase polymerase chain reaction (PCR).

RESULTS

SPIR inhibited the stimulated production of TNF-alpha, IL-6, and IFN-gamma, whereas the release of IL-1beta was not significantly affected. The SPIR-induced cytokine inhibition occurred at the transcriptional level and was independent of antimineralocorticoid and antiandrogen activities.

CONCLUSION

The findings suggest that inhibited production of proinflammatory cytokines may be an extrarenal mechanism that contributes to the beneficial effect of SPIR in patients with CHF.

Modulation of serum testosterone and autonomic function through stimulation of the male human vomeronasal organ (VNO) with pregna-4,20-diene-3,6-dione

In mammals, external chemosensory signals from conspecifics of the opposite sex acting on vomeronasal organ receptors can modulate the release of gonadotropins. There is developmental, anatomical and functional evidence showing that the human vomeronasal organ (VNO) has the characteristics of a chemosensory organ. We have been using naturally occurring human pheromones to serve as models for designing novel synthetic compounds that we call vomeropherins. In previous publications we reported that vomeropherin pregna-4,20-diene-3,6-dione (PDD) delivered to the VNO of normal female and male human volunteers significantly affected male subjects only, decreasing respiration and cardiac frequency, augmenting alpha brain waves, and significantly decreasing serum luteinizing hormone (LH) and follicle stimulating hormone (FSH). Results of the present work confirm that PDD produces a local dose-dependent effect in the male human VNO. This is followed by a mild parasympathomimetic effect characterized by 10% increase of vagal tone, together with decreased frequency of electrodermal activity events. Furthermore, PDD locally delivered to the male human VNO significantly decreases serum LH and testosterone (p < 0.01). The present results contribute additional evidence supporting the functionality of the human VNO and its repercussions in autonomic and psychophysiological functions, as well as in neuroendocrine secretions.

Inhibition of steroid sulfatase activity by danazol

The hydrolysis of dehydroepiandrosterone sulfate (DHAS) by human liver cells in culture and the hydrolysis of and formation of estradiol-17 beta (E2) from estrone sulfate (E1S) by human breast tumor preparations in vitro were studies in the presence and absence of danazol. In the latter tissue the effects of medroxyprogesterone acetate (MPA), trilostane, aminoglutethimide (AG) and tamoxifen were tested for comparison. Danazol at concentrations of 10(-6) - 1.4 X 10(-4) M strongly inhibited the hydrolysis of DHAS as well as the hydrolysis of and formation of E2 from E1S. With the exception of a slight inhibitory effect of trilostane upon E1S hydrolysis, the other four drugs did not inhibit the metabolism of E1S. Danazol, at concentrations corresponding to those occurring in vivo during therapy, is a potent inhibitor of steroid sulfatase activity. This may be one of the ways in which the drug affects peripheral and target tissue levels of steroid hormones.

Variation in conception rates following synchronization of estrus with melengestrol acetate and prostaglandin F2 alpha

Beef cows and heifers (n = 263) at three locations that were exhibiting estrous cycle either were fed .5 mg/d melengestrol acetate (MGA) for 7 d and administered prostaglandin F2 alpha (25 mg, i.m.) on the last day of MGA feeding or were untreated. State of the estrous cycle at the beginning of the experiment was determined based on estrous detection and (or) progesterone concentrations in pretreatment blood samples. Estrous was checked twice daily for 30 d posttreatment. Animals were artificially inseminated approximately 12 h after detection of estrus. A synchronized estrus (less than 7 d posttreatment) was detected in 72% of the treated animals. More animals in the treated group became pregnant during the first 7 d of breeding, but their conception rate was lower than that of animals in the control group (P less than .05). Conception rate (36%) was reduced among treated animals when MGA feeding began late (d 14 to 20) in the estrous cycle. Conversely, the conception rate (66%) of treated animals fed MGA beginning earlier in the cycle was not different from that of control animals (73%; treatment x stage of cycle; P less than .05).

Spironolactone and potassium canrenoate in normal man

The pharmacological activity of single doses of the two aldosterone antagonists, potassium canrenoate and spironolactone, was examined in two studies in healthy volunteers. Both drugs were active in reversing urinary electrolyte changes induced by fludrocortisone in periods 2 to 16 hr after treatment. Potassium canrenoate was significantly less potent that spironolactone on a weight or molar basis, with best estimates of the relative potency potassium canrenoate: spironolactone of approximately 0.3:1. On a weight basis the two drugs yielded plasma levels of the metabolite canrenone which were approximately equivalent. The results indicate that canrenone is not the principal pharmacologically active metabolite of spironolactone. Our study suggests that a major part of the renal antimineralocorticoid activity of spironolactone may be attributable to minor sulfur-containing metabolites or their precursors having a high renal clearance that affords access to their site of activity via the renal tubular fluid.

Profound alterations of the lipoprotein metabolism during danazol treatment in premenopausal women

Twelve women with pelvic endometriosis were treated with 600 mg of danazol daily for 24 weeks. The molar and fractional lecithin:cholesterol acyl transfer (LCAT) rates and the concentrations of cholesterol, phospholipids, and triglycerides were determined in plasma and in the very low-density lipoprotein, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and HDL2 and HDL3 fractions before, during, and after the medication. After 2 weeks the HDL, HDL2, and HDL3 cholesterol concentrations were reduced by 49%, 73%, and 29%, respectively, while the LDL level was increased by 14%. The molar and fractional LCAT rates decreased during treatment, and these reduced LCAT rates are consistent with a reduced fractional LDL removal. Within 8 weeks after cessation of medication, all parameters had returned to the pretreatment levels.

Conception rate in Bos taurus and Bos indicus crossbred heifers after postweaning energy manipulation and synchronization of estrus with melengestrol acetate and fenprostalene

Conception rate in heifers after synchronization of estrus with melengestrol acetate (MGA) and fenprostalene (a prostaglandin F2 alpha analogue; PGF) was determined in pubertal Bos taurus and Bos indicus crossbred yearling heifers. Angus x Hereford (AH, n = 137) and Brahman x Hereford (BH, n = 97) heifers were sorted by body weight after weaning into light (LW) and heavy (HW) weight blocks. Heifers were assigned by age to diets to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weight by the start of breeding. Heifers that exhibited estrus and had serum progesterone greater than or equal to 1 ng/ml (0 or 10 d before estrous synchronization treatment) were assigned randomly within breed and nutritional groups to either an estrous synchronization (S) or control (C) group. Heifers in the S group were fed .5 mg of MGA for 7 d and injected s.c. with 2 mg PGF on d 7 of MGA. All heifers were inseminated 12 h after first detected estrus. A greater proportion of AH (P less than .01) than of BH heifers were in estrus within 6 d after PGF, and more S heifers than C heifers (P less than .01) were in estrus. Conception rate at first service was proportionately higher (P less than .001) in AH than in BH heifers and lower (P less than .02) in S than in C heifers. There was a breed x energy level interaction (P less than .01) for conception rate at first service. Stage of the estrous cycle at the time treatment with MGA was initiated influenced (P less than .05) conception rate at first service in the S, AH heifers, with lower conception rates among heifers beginning treatment late in their estrous cycles (greater than or equal to d 12). Pregnancy rates after 21 d were higher (P less than .01) in AH than in BH heifers and higher (P less than .01) in HW than in LW heifers. More HE than LE heifers (P less than .02), and more AH than BH heifers were pregnant after 45 d. Pregnancy rates at the end of 21 d were higher among HE, BH heifers than among LE contemporaries. A higher (P less than .02) percentage of HE, HW, BH heifers were pregnant at the end of 45 d compared with other BH groups. Results indicated that a 7-d MGA-PGF treatment reduced conception rates at first service in pubertal yearling heifers. Pregnancy rate was affected by prebreeding nutrition in BH yearling heifers at the end of 45 d.

The selective antimuscarinic action of stercuronium

1 The antimuscarinic activity of stercuronium, a competitive neuromuscular blocking drug, has been compared in the anaesthetized guinea-pig, guinea-pig atria, bladder and ileum, rabbit atria and the sympathetically innervated rabbit ear artery preparation using carbachol (CCh) as agonist.2 In the anaesthetized guinea-pig, stercuronium (0.2 and 2.0 mumol/kg) produced significantly greater inhibition (P < 0.05) of the bradycardia than of the vasodepressor response produced by CCh, the difference being 2 fold at the low dose and 5.8 fold at the higher dose.3 In guinea-pig atria the negative chronotropic response to CCh was inhibited to a similar degree to the negative inotropic response by stercuronium, whereas in bladder and ileum stercuronium was 17 fold less active as an antimuscarinic drug.4 The affinity of stercuronium for the prejunctional muscarinic receptor on sympathetic nerve endings in the rabbit ear artery was similar to that for the muscarinic receptor mediating negative inotropic responses to CCh in the rabbit left atrium, and 2.3 fold less than the affinity for the muscarinic receptors in guinea-pig atria.5 A similar trend was observed with gallamine, another neuromuscular blocking drug, when results obtained in the rabbit ear artery preparation were compared to previously reported data. Also, the affinity of gallamine for muscarinic receptors mediating relaxation of the cat anococcygeus muscle was found to be similar to that for prejunctional muscarinic receptors in the rabbit ear artery.6 It is suggested that stercuronium and gallamine have a greater affinity for cardiac receptors and the inhibitory muscarinic receptors on sympathetic nerve endings than for muscarinic receptors mediating contraction of bladder and ileum.

Progestational activity of danazol in the human female subject

A progestational action of Danazol has not been reported in the human subject. Danazol administration for 1 month suppressed serum FSH and estradiol values, and the midcycle LH surge; ovulation promptly resumed after treatment. Administration to patients with polycystic ovarian disease resulted in increased LH values, elevated basal temperature, secretory findings in the endometrial biopsy, and menses. Ovarian biopsy did not document corpus luteum formation, and plasma progesterone did not rise. Administration of Danazol to an ovariectomized patients pretreated with estrogen resulted in an atypical endometrial secretory change. Clinical responses to Danazol may in part be explained by a progestational-like effect of the drug.