Effects of castration of immature rats on serum FSH and LH, and of various steroid treatments after castration

New perspectives on sex differences in learning and memory

Females have historically been disregarded in memory research, including the thousands of studies examining roles for the hippocampus, medial prefrontal cortex, and amygdala in learning and memory. Even when included, females are often judged based on male-centric behavioral and neurobiological standards, generating and perpetuating scientific stereotypes that females exhibit worse memories compared with males in domains such as spatial navigation and fear. Recent research challenges these dogmas by identifying sex-specific strategies in common memory tasks. Here, we discuss rodent data illustrating sex differences in spatial and fear memory, as well as the neural mechanisms underlying memory formation. The influence of sex steroid hormones in both sexes is discussed, as is the importance to basic and translational neuroscience of studying sex differences.

Decellularized human ovarian scaffold based on a sodium lauryl ester sulfate (SLES)-treated protocol, as a natural three-dimensional scaffold for construction of bioengineered ovaries

BACKGROUND

The increasing number of patients with ovarian insufficiency due to autoimmune disorders, genetic predisposition, or iatrogenic effects of treatment such as cancer therapies necessitates an urgent measure to find a safe and transplantable alternative ovary. A bioengineered ovary is one of the strategies on which the researchers have recently been working. An engineered ovary should be able to mimic the natural ovary aspects. Recent studies suggest that the decellularized organ-specific extracellular matrix-based scaffolds can serve as a native niche to bioengineering artificial organs. Therefore, we established a human decellularized ovarian scaffold based on a sodium lauryl ester sulfate (SLES)-treated process, as an optimized protocol.

METHODS

The human ovary samples were decellularized with 1% SLES for 48 h followed by DNase I in PBS for 24 h, and then thoroughly rinsed in PBS to remove the cell remnants and chemical reagents. Efficient cell removal was confirmed by DNA content analysis, hematoxylin and eosin, and Hoechst staining. Preservation assessment of the extracellular matrix structures was performed by immunohistochemistry, histological staining, and scanning electron microscopy. An MTT test was done to assess the in vitro scaffold's cytocompatibility, and finally in vivo studies were performed to evaluate the biocompatibility, bioactivity, and secretion functions of the ovarian grafts made of primary ovarian cells (POCs) on the decellularized scaffolds.

RESULTS

Evidence provided by SEM, histochemical, and immunohistochemical analyses showed that the ovarian extracellular matrix was preserved after decellularization. Moreover, MTT test indicated the suitable cytocompatibility of the scaffolds. The in vivo assessment showed that the POCs kept their viability and bioactivity, and reconstructed the primordial or primary follicle-like structures within the scaffolds after transplantation. Immunostaining characterized somatic cells that were capable of expressing steroid hormone receptors; also, as a marker of granulosa cell, inhibin-α immunostaining demonstrated these cells within the grafts. Additionally, hormone assessment showed that serum estradiol and progesterone levels were significantly higher in ovariectomized rats with ovarian cells-seeded grafts than those with or without decellularized scaffold grafts.

CONCLUSIONS

A human ovary-specific scaffold based on a SLES-decellularized protocol as a biomimicry of the natural ovarian niche can be an ideal scaffold used to reconstruct the ovary.

Changes in dendritic architecture: not your "usual suspect" in control of the onset of puberty in male rats

Until the recent past, the search for the underlying drive for the pubertal increase in gonadotropin-releasing hormone (GnRH) hormone from the GnRH-containing neurons in the hypothalamus was largely focused on extrinsic factors. The most recent evidence however indicates changes in the structure of GnRH neurons themselves may contribute to this fundamental event in development. Based on our studies in males, dendritic architecture is not static from birth until adulthood. Instead, dendrites undergo a dramatic remodeling during the postnatal period which is independent of testosterone and occurs before the pubertal increase in GnRH release. First, the number of dendrites emanating from somata is reduced between infancy and adulthood. Moreover, a dendrite of adult GnRH neurons invariability arises at angle of 180°from the axon as opposed to the extraordinary variability in location during infancy. In fact, in some neurons from infants, no dendrite even resides in the adult location. Thus, there is a spatially selective remodeling of primary dendrites. Secondly, dendrites of GnRH neurons from infants were highly branched prior to assuming the compact morphology of adults. Finally, other morphological aspects of GnRH neurons such as total dendritic length, the numbers of dendrite branches and the lengths of higher order branches were significantly greater in infants than adults, indicating a consolidation of dendritic arbors. Activity in multi-compartment models of GnRH neurons, suggest the impact of structure on neuronal activity is exerted with both active and passive dendrites. Thus, passive properties make a defining contribution to function. Accordingly, changes in morphology alone are likely to have functional consequences for the pattern of activity in GnRH neurons. Our findings suggest structural remodeling of dendrites during the postnatal period likely facilitates repetitive action potentials and thus, GnRH release at the time of puberty.

Hirsutism, virilism, polycystic ovarian disease, and the steroid-gonadotropin-feedback system: a career retrospective

This career retrospective describes how the initial work on the mechanism of hormone action provided the tools for the study of hirsutism, virilism, and polycystic ovarian disease. After excessive ovarian and or adrenal androgen secretion in polycystic ovarian disease had been established, the question whether the disease was genetic or acquired, methods to manage hirsutism and methods for the induction of ovulation were addressed. Recognizing that steroid gonadotropin feedback was an important regulatory factor, initial studies were done on the secretion of LH and FSH in the ovulatory cycle. This was followed by the study of basic mechanisms of steroid-gonadotropin feedback system, using castration and steroid replacement and the events surrounding the natural onset of puberty. Studies in ovariectomized rats showed that progesterone was a pivotal enhancer of estrogen-induced gonadotropin release, thus accounting for the preovulatory gonadotropin surge. The effects of progesterone were manifested by depletion of the occupied estrogen receptors of the anterior pituitary, release of hypothalamic LHRH, and inhibition of enzymes that degrade LHRH. Progesterone also promoted the synthesis of FSH in the pituitary. The 3α,5α-reduced metabolite of progesterone brought about selective LH release and acted using the GABA(A) receptor system. The 5α-reduced metabolite of progesterone brought about selective FSH release; the ability of progesterone to bring about FSH release was dependent on its 5α-reduction. The GnRH neuron does not have steroid receptors; the steroid effect was shown to be mediated through the excitatory amino acid glutamate, which in turn stimulated nitric oxide. These observations led to the replacement of the long-accepted belief that ovarian steroids acted directly on the GnRH neuron by the novel concept that the steroid feedback effect was exerted at the glutamatergic neuron, which in turn regulated the GnRH neuron. The neuroprotective effects of estrogens on brain neurons are of considerable interest.

Spatially selective, testosterone-independent remodeling of dendrites in gonadotropin-releasing hormone (GnRH) neurons prepubertally in male rats

Adult GnRH neurons exhibit a stereotypic morphology with a small soma, single axon, and single dendrite arising from the soma with little branching. The adult morphology of GnRH neurons in mice reflects an anatomical consolidation of dendrites over postnatal development. We examined this issue in rat GnRH neurons with biocytin filling in live hypothalamic slices from infant males, as adult littermates and in gonad-intact males, castrated males, and in males with one of three levels of testosterone (T) treatment. Somatic area and total dendritic length were significantly greater in infant males than in adults. Moreover, total numbers of dendrite branches were greater in infant males as compared with adults. The number of higher order branches and the lengths of higher order branches were also greater in infant males than in adults. Most interestingly, in adults a single dendrite arose from the somata, consistently at 180° from the axon. In contrast, prepubertal animals had an average of 2.2 ± 0.2 primary dendrites arising from somata (range, one to seven primary dendrites). Angles relative to the axon at which dendrites in prepubertal males emanated from GnRH somata were highly variable. Castration at 25 d of age and castration at 25 d of age with one of three levels of T treatment did not influence morphological parameters when GnRH neurons were examined between 40 d and 48 d of age. Thus, a spatially selective remodeling of primary dendrites and consolidation of distal GnRH dendritic arbors occurs during postnatal development and is largely independent of T.

Neuroendocrine consequences of androgen excess in female rodents

Androgens exert significant organizational and activational effects on the nervous system and behavior. Despite the fact that female mammals generally produce low levels of androgens, relative to the male of the same species, increasing evidence suggests that androgens can exert profound effects on the normal physiology and behavior of females during fetal, neonatal, and adult stages of life. This review examines the effects of exposure to androgens at three stages of development--as an adult, during early postnatal life and as a fetus, on reproductive hormone secretions in female rats. We examine the effects of androgen exposure both as a model of neuroendocrine sexual differentiation and with respect to the role androgens play in the normal female. We then discuss the hypothesis that androgens may cause epigenetic modification of estrogen target genes in the brain. Finally we consider the clinical consequences of excess androgen exposure in women.

Effect of particle size on the prolonged action of subcutaneous danazol in male and female rats

OBJECTIVE

To investigate the effects of two different particle sizes of danazol in male and female rats.

DESIGN

Prospective, vehicle-controlled study.

SETTING

Undergraduate college research facility and medical research laboratory.

ANIMALS

18 castrated male rats and 18 cycling female rats.

INTERVENTION(S)

Preparations of danazol with particle sizes of 2.05 microm or 5.2 microm were administered as a single subcutaneous injection of 400 mg/kg to castrated male rats or estrus-cycling females.

MAIN OUTCOME MEASURE(S)

Serum LH level in males and estrous cycle length in females.

RESULT(S)

In males, both preparations significantly (P<. 001) suppressed serum LH by day 5 of treatment. Gonadotropin levels remained low throughout the 35-day study in rats that received the larger-particle danazol, whereas LH levels began to increase after 25 days in rats that received smaller-particle danazol. In females, the normal 4- to 5-day estrous cycle interval was prolonged to 38.7 days (P<.001) in those that received the larger-particle danazol and 25.5 days in those that received the smaller-particle danazol.

CONCLUSION(S)

The results demonstrate the prolonged effectiveness of a single subcutaneous dose of danazol and indicate that one might be able to predict the effective duration of activity by changing the particle size of the danazol administered.

Danazol: prolonged suppression of gonadotropins after subcutaneous administration in the castrate male rat

OBJECTIVE

Our purpose was to compare oral versus subcutaneous administration of danazol for its effect on elevated serum luteinizing hormone and follicle-stimulating hormone levels in castrated male rats.

STUDY DESIGN

A single dose of danazol, either 100 or 400 mg/kg, was administered by gastric intubation or injected subcutaneously. Jugular venipuncture blood samples were taken at 0, 3, 24, and 48 hours and at 7, 10, 15, and 25 days, and serum levels of luteinizing hormone and follicle-stimulating hormone were determined by radioimmunoassay.

RESULTS

Gonadotropin levels returned to control values 96 hours after oral administration, whereas 400 mg/kg of danazol administered subcutaneously resulted in suppression of gonadotropins for 25 days.

CONCLUSIONS

Subcutaneous administration of danazol results in an unexpectedly prolonged suppression of serum gonadotropins compared with the same dose administered orally. A change from oral administration to a prolonged-release subcutaneous preparation of danazol may enhance the use of this drug in clinical situations and may lessen undesirable side effects.

High-dose gestagens modulate bone resorption and formation and enhance estrogen-induced endosteal bone formation in the ovariectomized mouse

To determine if gestagens of two separate classes have differing skeletal actions, we studied the effects of pharmacologic doses of norethisterone acetate (NETA), a 19-nortestosterone, and megestrol acetate (MA), a 17 alpha-hydroxyprogesterone, on bone formation and resorption in intact and in ovariectomized mice. In the same set of experiments, we also attempted to determine if these gestagens can alter the skeletal activity of 17 beta-estradiol (E2). Experimentally, the skeletons of 78 female BALB/c mice were prelabeled with [3H]tetracycline (3H-T). The animals were randomized to 13 groups of 6 mice each 3 days after the final 3H-T injection. Ovariectomies (OVX) were performed on 8 groups and sham operations (SO) on 5 groups. To study the skeletal effects of the gestagens, 4 groups each of the OVX and SO mice were treated with controlled-release pellet implants calculated to deliver 80 or 250 micrograms of NETA or MA per day. To study gestagen interactions with E2, 3 groups of OVX mice were treated with either 40 micrograms/day of E2 or 40 micrograms/day of E2 plus 250 micrograms/day of NETA or MA. One group of OVX and one group of SO animals received placebo pellets. Fluorochrome labels were administered 10 and 11 and 3 and 4 days before sacrifice to allow histomorphometric evaluation of bone formation. At the end of the 60 day protocol, tibiae and thoracic vertebrae were removed and processed for quantitating the levels of bone resorption based on the amounts of 3H-T retained in the bones. The femora were fixed and embedded for comparison of diaphyseal bone histomorphometry, and the humeri and lumbar vertebrae were prepared for bone density determinations. Reflecting an increase in bone resorption, 3H-T levels in tibiae and vertebrae were decreased in placebo-treated OVX animals compared to the placebo-treated SO group (p < 0.01). Treatment of both SO and OVX mice with NETA decreased bone resorption in a dose-dependent manner, but MA had no significant effects on vertebral bone resorption and increased bone resorption in the tibiae (p < 0.01). E2 treatment of OVX mice reduced bone resorption, but there were no significant interactions between the E2 and gestagen treatments on resorptive activity. Based on bone histomorphometry of in vivo fluorochrome labels, both gestagens increased periosteal bone formation rates but had no effect on endosteal bone formation (BFRe). In contrast, E2 treatment of the OVX mice stimulated bone formation at the endosteal surface.(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulatory and inhibitory effects of progesterone on FSH secretion by the anterior pituitary

The purpose of this study was to investigate whether progesterone exerted progesterone receptor mediated direct effects on the anterior pituitary in the secretion of FSH and whether such effects were mediated through the 5 alpha-reduction of progesterone. Treatment of anterior pituitary dispersed cells for 48 h with 0.5 nM estradiol reduced the ED50 for gonadotropin releasing hormone (GnRH)-stimulated FSH release from 0.58 to 0.36 ng/ml and the ED50 for GnRH-induced LH release from 0.54 to 0.19 ng/ml. When dispersed pituitary cells were treated with 0.5 nM estradiol and exposed to various doses of progesterone for 1 to 6 h, the most consistent rise in basal and GnRH-stimulated FSH release was observed with the 50 nM dose of progesterone with a 3-h exposure period. All three doses of progesterone elevated basal LH and GnRH-stimulated LH was increased by the 50 and 100 nM doses of progesterone during the 3-h period of treatment. Using the 50 nM dose of progesterone, basal and GnRH-stimulated LH was increased after 2, 3 and 6 h of progesterone treatment. When the period of exposure of progesterone was extended to 12, 36 or 48 h, there was a significant inhibition of GnRH-stimulated FSH release. GnRH-stimulated LH release was inhibited at 36 and 48 but not 12 h after progesterone treatment. These studies showed that the effect of progesterone administered for periods of 1 to 6 h enhanced the secretion of LH and FSH whereas progesterone administered for periods beyond 12 h inhibited FSH and LH release by dispersed pituitary cells in culture. These results are similar to those observed in vivo after progesterone treatment. Furthermore estrogen priming of the dispersed pituitary cells was necessary to observe the effects of progesterone. The progesterone antagonist RU486 prevented the progesterone-induced rise in GnRH-stimulated FSH release. Furthermore the 5 alpha-reductase inhibitor N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane- 17 beta-carboxamide also prevented the progesterone-induced rise in GnRH-stimulated FSH release in estrogen-treated dispersed pituitary cells. These results indicate that the anterior pituitary is a major site of action of progesterone in the release of FSH and that 5 alpha-reduction of progesterone plays an important role in FSH release.

Inhibitory and stimulatory actions of danazol in rat ovarian and uterine tissues

We examined whether danazol has a direct action on ovarian steroid secretion and/or uterine prostaglandin (PG) F2 alpha catabolic activity in immature rats in which the first ovulation was induced and in adult ovariectomized rats. The preovulatory surge of estradiol and progesterone was markedly suppressed together with that of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by danazol administration under conditions that blocked the first ovulation. Uterine weight and PGF2 alpha catabolic activity enhanced by endogenous estrogen were greatly decreased by danazol treatment at a dose that did not block the first ovulation in immature rats. When danazol (30 mg) was given s.c. once daily for 2 days to ovariectomized rats, the uterine weight and PGF2 alpha catabolic activity per uterus were clearly increased, and the compensatory increase in FSH levels as a result of castration was not influenced, although the compensatory increase in LH levels was inhibited. These results demonstrate that danazol has a direct action on the ovary and uterus, and give further support to the view put forward in our previous paper that these actions of danazol may contribute to its therapeutic effects.

Effects of an androgenic derivative on pre-established mammary tumours chemically induced in the rat

The effects were studied of an androgenic derivative--danazol--administered at doses of 10-12 mg kg-1 day-1 during 97 days to rats with dimethylbenz[a] anthracene-induced mammary tumours. Our main observations were as follows. (a) Danazol did not influence ovarian function at the end of the assay. (b) The treatment with danazol reduced the incidence (P less than 0.05), number of tumours (P less than 0.05) and volume of malignant mammary tumours; on the other hand, the values of these parameters for benign tumours and those of doubtful expression were similar in both experimental groups. (c) Such differential action of Danazol seems to be due to the different incidence and/or content of receptors of both types of tumours. (d) The latter results lead to a hypothesis for the mechanism of action of danazol based on its behaviour at different levels.

Inhibition of the first ovulation and ovarian prostaglandin F2 alpha metabolism by danazol in rats

The present study was conducted to investigate the mode of action of danazol by monitoring the first ovulation, serum luteinizing hormone (LH) levels and ovarian prostaglandin (PG) F2 alpha metabolism in pregnant mare serum gonadotropin (PMSG)-primed immature female rats. When danazol (750 mg/kg) was given p.o. once a day for 5 days (day 24-28), the occurrence of the first ovulation, the increase in capacity to form 13,14-dihydro-PGF2 alpha and PGF2 alpha levels induced by PMSG (5 IU) injected on day 26 were clearly inhibited on day 29. Danazol also markedly suppressed the LH surge occurring on day 28. Although the danazol-induced blockage of ovulation was restored by injection of human chorionic gonadotropin, the number of oocytes was significantly decreased as compared with that of controls. The present data indicate that the inhibitory actions of danazol on ovulation and ovarian PGF2 alpha metabolism may occur via some direct effects on the ovary in addition to the suppression of gonadotropin release from the pituitary gland.

A randomized, prospective comparison of endocrine changes induced with intranasal leuprolide or danazol for treatment of endometriosis

A prospective, randomized trial compared hormonal changes induced with intranasal leuprolide 1.6 mg/day to danazol 800 mg/day for treatment of endometriosis. Both regimens induced anovulation and ovarian suppression in all subjects. Mean estradiol (E2) and progesterone (P) levels were suppressed with both regimens, but were lower with leuprolide. There was no difference in cumulative follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels, although at times during treatment mean levels of these hormones were lower with leuprolide. Higher P levels in the danazol group, most likely of adrenal origin, indicated a suppressive effect on adrenal steroidogenesis. Symptomatic improvement was significant in both groups. Laparoscopy after treatment also demonstrated a decrease in endometriosis scores in both groups. At 12 months after treatment, cumulative pregnancy and live birth rates were similar in both groups. Leuprolide offers an attractive alternative to danazol for the medical treatment of endometriosis.

Selective modulation of FSH and LH secretion by steroids

Significant divergence between the pattern of FSH and LH secretion has been observed in the ovulatory cycle, after ovariectomy and during puberty. The presence of an FSH-releasing factor, gonadal FSH inhibiting and releasing peptides and changes in the pulsatile pattern of LHRH secretion are among the postulates used to explain the divergent secretion of FSH and LH. Experiments in our laboratory have shown considerable evidence of differential regulation of FSH and LH secretion by steroids in the absence of gonadal regulatory peptides. Natural and synthetic estrogens show significant differences in the suppression of FSH and LH in the ovariectomized rat using a standard uterine response to the estrogen as the end point. In the immature ovariectomized rat treated with a low dose of estradiol that is sufficient for the synthesis of progesterone receptors to ensure progesterone sensitivity, but not large enough to induce estrogen triggered LH surges, progesterone administration resulted in a pattern of LH and FSH secretion similar to that observed on the day of proestrus in the cycling rat. Selective secretion of FSH was induced in the estrogen primed immature rat model by the administration of progesterone metabolite 5 alpha-dihydroporgesterone (5 alpha-DHP) while selective LH secretion was induced by 3 alpha, 5 alpha-tetrahydroprogesterone (3 alpha,5 alpha-THP). The selective secretion of FSH and LH induced by progesterone metabolites was confirmed in the immature female rat primed with PMSG and maintained in constant light. 5 alpha-DHP was also able to induce a greater release of FSH when administered to the adult cycling rat on proestrus. The priming of the pituitary gonadotrope in secreting a high baseline level of FSH or responding to LHRH in releasing a greater amount of FSH appeared to be an important factor in selective FSH release and such priming can be brought about by 5 alpha-DHP in the absence of gonadal regulatory peptides.

Danazol inhibits steroidogenesis by the human ovary in vivo

Gonadotropins, estradiol (E2), and the steroid precursors of ovarian estrogen secretion were examined in women on danazol to clarify actions of the medication on hypothalamic-pituitary-ovarian function. Follicle-stimulating hormone was not altered acutely after a single maximal dose or chronically during therapy, whereas a slight but significant increase in luteinizing hormone was noted during the 6 months of treatment. During danazol treatment, there was a blunted response of E2 to injections of human menopausal gonadotropins. The progestin and androgen precursors of E2 were reduced, with the exception of 17-hydroxypregnenolone, which was significantly increased. This 17-hydroxylase enzyme block persisted in spite of dexamethasone suppression of adrenal function. Therefore, the reduced ovarian secretion of E2 in women receiving danazol is due in part to reductions of ovarian precursor steroids for E2 synthesis, consequent to a direct ovarian action of the medication.

Cytoplasmic and nuclear estrogen binding capacity in the rat uterus during treatment with danazol and testosterone

Danazol, testosterone and dihydrotestosterone (DHT) were tested as competitors for estrogen receptors on immature rat uterus cytosol. No competitive binding could be demonstrated for any of these steroids. After that, prepubertal Wistar rats were exposed to danazol, testosterone or propylene glycol (control) for 3 days or 17 days. After the appropriate exposure to medication, the animals were killed. Both danazol and testosterone appeared to be uterotropic after 3 days of treatment, although the increase in the uterine weight was significant only in the danazol-treated group (p less than 0.05). This effect was lost after 17 days of treatment. Estradiol receptor binding assays were done on the cytosolic and nuclear fractions of the homogenized uterine tissue of each group. The estrogen binding capacity of cytosols was increased in both the danazol (p less than 0.05) and the testosterone (p less than 0.01) groups after 3 days of treatment. A parallel increase was found in the nuclear fraction of both groups. After 17 days of treatment, the comparison between the 3 groups showed no differences in the cytosolic or nuclear estrogen binding capacity. The information provided by this study suggests that some effects of danazol may be due to an androgenic action and that may be associated to increases in the free fraction of testosterone.

Correlation between LH and estrogen receptor turnover in pituitary and hypothalamus of castrate rats following estrogen agonists and antagonists

A series of studies was undertaken to correlate the short-term dynamics of LH secretion and depletion-replenishment patterns of estrogen receptors (ER) in hypothalamic and pituitary cytosols of ovariectomized rats. Animals castrated for 2 weeks were administered various test compounds and analyzed at 1, 3, 5, 10 and 15 h post-treatment. A single injection of 10 micrograms 17 beta-estradiol (E2) to ovariectomized rats elicited a rapid depletion of ER in both pituitary and hypothalamus and a dramatic, though delayed, fall in serum LH. ER replenishment occurred in both tissues through 15 h and LH recovered in a similar manner. When cycloheximide was administered along with E2, ER replenishment was completely inhibited in both tissues; serum LH fell and failed to recover. Actinomycin D injected with E2 blocked replenishment in pituitary but not hypothalamus; serum LH recovered in parallel with the hypothalamic ER pattern. 17 alpha-E2 elicited only slight changes in ER and LH was suppressed 10-20% through 15 h. CI-628 caused a near total depletion of pituitary ER with no subsequent replenishment, whereas hypothalamic ER content was virtually unaltered; serum LH was suppressed and later recovered. Orchidectomized rats given 5 micrograms E2 demonstrated a less complete ER depletion in hypothalamus, and an earlier replenishment than that seen in pituitary or hypothalamus of similarly treated ovariectomized females. Serum LH rebounded to 157% of control levels at 15 h. The results indicate that the acute feedback suppression of LH by exposure to estrogens correlates with binding to ER and nuclear translocation. Replenishment and/or retention of cytoplasmic ER in hypothalamus appears to be required for full resumption of LH secretion, following acute suppression.

Danazol treatment of advanced prostate cancer: clinical and hormonal effects

Danazol was administered to 19 patients with advanced prostate cancer. These patients were treated for periods ranging from 3 days to 18 weeks. There were no objective remissions, but three patients (15.8%) had objectively stable disease (N.P.C.P. criteria) with complete pain control for periods ranging 15-18 weeks. Seven patients experienced tumor flare reactions, one requiring withdrawal of treatment and one resulting in rapid clinical deterioration and death. Four other patients died within 3 weeks and, although they were already in the terminal phase of disease when treatment commenced, it is possible that the deaths were treatment related. This study indicates that danazol has only limited activity in the treatment of advanced prostate cancer and is associated with a high incidence of tumor flare reactions with the risk of rapid clinical deterioration.

Effects of estradiol and estradiol-progesterone treatment on gonadotropin secretion in castrate aging female rats

Estradiol-17 beta and estradiol-17 beta-progesterone were administered to aging female rats immediately after castration. Estradiol (1.6 micrograms) alone suppressed the castration hypersecretion of FSH in mature animals to 70% of the castration controls, but in 360-day-old and older animals, the inhibition was less than 10%. There was a decrease in the castration hypersecretion of LH by exogenous estradiol-17 beta with increasing age, but the pattern of suppression was similar in all animals, regardless of age. When a constant dose of estradiol-17 beta of 0.4 micrograms/kg body wt. was administered to castrate rats with varying doses of progesterone, it was shown that after 270 days of age the negative feedback effect of these steroids on FSH secretion was not found. Whereas, when progesterone of varying doses was administered with a constant dose of 0.8 micrograms/kg BW of estradiol-17 beta, it was shown that after 180 days of age the positive feedback effect of these steroids on FSH was absent. After 270 days of age the augmentation of LH secretion by estradiol-17 beta and a middle dose of progesterone was not apparent even though the negative feedback on LH was effective. A defect in positive and negative feedback effects of gonadal steroids on gonadotropin secretion may be causative to age-related changes in the estrous cycle of rats.

Hot flashes in postmenopausal women ameliorated by danazol

Six postmenopausal women with hot flashes were studed for two 8-week periods during which they received low-dose danazol (100 mg/24 hours) for one time interval and placebo for the other in a randomized double-blind manner. The patients recorded the number and severity of their hot flashes daily. On the last day of each period the patients were admitted to the research center overnight for an 8-hour monitoring of forehead skin temperatures and for continuous withdrawal of blood to determine 20-minute integrated levels of luteinizing hormone. Three of the six patients responded to danazol with a mean reduction of 88% in the number of hot flashes and a 53% decrease in the severity of hot flashes. Responders differed from nonresponders in that on treatment the frequency of nocturnal pulses of luteinizing hormone was reduced more (36.1% versus 14.4%), the increase in amplitude of the pulses was greater (+30.7% versus -11.8%), and the fall in the mean level of luteinizing hormone was more marked (19.0% versus 10.5%). The findings suggest that danazol may be a reasonable alternative to estrogen in the treatment of postmenopausal women with severe vasomotor symptoms.

Effects of gonadectomy and sex steroids on pituitary gonadotrophin release and response to gonadotrophin-releasing hormone (GnRH) agonist in the bullfrog, Rana catesbeiana

Gonadectomy of adult bullfrogs, Rana catesbeiana, elevated plasma levels of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Profiles of plasma gonadotrophins after gonadectomy were similar in the two sexes; however, FSH increased faster in females than males. Both gonadotrophins continued to rise for several months and remained elevated after 1 year, but there was some dissociation between the two hormones; FSH increased sooner (1 week vs 3 weeks), reached higher levels (FSH/LH much greater than 1), and did not show the secondary decline exhibited in LH. Similarly, in subadult males and females, gonadectomy increased plasma FSH by 1 week but LH levels were less affected. Postgonadectomy increases in both gonadotrophins were prevented by chronic (6-week) implantation of capsules containing estradiol-17 beta (E2) or 5 alpha-dihydrotestosterone (DHT), and treatment with DHT and E2 within physiological ranges starting 1 year after gonadectomy also suppressed chronically elevated levels of plasma gonadotrophins. Compared to untreated gonadectomized frogs, the rate of increase in both plasma gonadotrophins. Compared to untreated gonadectomized frogs, the rate of increase in both plasma gonadotrophins was accelerated after removal of DHT at 6 weeks. Acute pituitary responsiveness to a gonadotrophin-releasing hormone (GnRH) agonist was markedly reduced in short-term (3.5-8 weeks) gonadectomized subadult males (but not females) and in long-term (1 year) gonadectomized males and females. Treatment with E2 had no effect on GnRH responsiveness in these frogs, but DHT implants significantly enhanced the response to agonist in both sexes. Thus, the nonaromatizable androgen--DHT--may have both negative feedback effects (at the hypothalamic level) and positive effects at the level of the pituitary, whereas, estrogen exhibited only the former, negative feedback activity. Sex differences in circulating DHT, which are detectable even in juveniles, may account for the sexual dimorphism in pituitary responsiveness to GnRH in the bullfrog.

The interaction of human endometrial and myometrial steroid receptors with danazol

The affinity of danazol for oestrogen, androgen and progesterone receptors in human endometrium and myometrium was determined, to study the mechanism of action of this drug in the treatment of endometriosis. The ability of danazol to combine with each of the three types of receptor was similar in both endometrium and myometrium. The capacity of danazol to compete with oestradiol-17 beta for the oestrogen receptor was very low (1.72 +/- 0.48 X 10(-3%) cross reaction, mean +/- SEM) and danazol, at the maximum concentration used, was unable to saturate the receptor; but danazol's ability to compete with progesterone for its receptor was considerably higher (8.41 +/- 1.65% using progesterone, 1.95 +/- 0.41% using R5020) and was saturable. Danazol was also able to displace dihydrotestosterone from the cytosol androgen receptor (6.29 +/- 1.82% cross reaction). The association constant of oestradiol for the endometrial and myometrial oestrogen receptors was 2.19 X 10(9)M-1 and 7.45 X 10(9)M-1 respectively, while that of progesterone and dihydrotestosterone for their receptors was similar in endometrium and myometrium (mean 0.25 +/- 0.06 X 10(9) M-1 and 3.62 +/- 1.67 X 10(9) M-1 respectively). Using R5020, the association constant for the myometrial progesterone receptor was 2.50 +/- 0.73 X 10(9) M-1. We conclude that, in view of the high circulating levels of danazol present in patients being treated for endometriosis, it is possible that danazol may bind to, and partly saturate, endometrial and myometrial oestrogen, progesterone and androgen receptors during treatment. An explanation may thus be provided for some of the diverse actions of this drug.

Effects of danazol on pulsatile gonadotropin patterns and on serum estradiol levels in normally cycling women

The effect of danazol on pulsatile luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2) secretion was examined in eight premenopausal women by serial blood sampling on day 10 of the control and first treatment cycles and during 2 subsequent months of treatment. The mean frequency of LH pulses decreased, while the mean pulse amplitude and increment increased (P less than 0.05). The mean LH concentrations were significantly suppressed in four of eight subjects. The mean frequency of E2 pulses, mean increment, and mean integrated area were decreased (P less than 0.05). The mean integrated FSH area did not change significantly during treatment, and we were not able to demonstrate unequivocal FSH pulses. We conclude that danazol in premenopausal women (1) lowers serum E2 concentrations by decreasing the frequency and increment of E2 pulses, (2) prevents compensatory gonadotropin rise, and (3) lowers the frequency but increases the amplitude and increment of LH pulses. The latter change reflects probably divergent effects of the drug on the pituitary and hypothalamus and results in an inconsistent lowering of basal LH levels.

Danazol in the treatment of endometriosis: analysis of 100 cases with a 4-year follow-up

A prospective study to evaluate the efficacy of danazol in the treatment of endometriosis was initiated in 1976. One hundred patients with endometriosis, as demonstrated by laparoscopy, were entered into the study. The mean length of patient follow-up was 49 months. All patients were treated with 800 mg of danazol per day. The mean duration of danazol therapy was 17.3 weeks. Eighty-nine percent of the patients reported symptomatic improvement, and 94% were improved, as demonstrated by repeat laparoscopy or laparatomy. After completing a course of danazol therapy, 57% of the patients underwent conservative laparotomy for fertility enhancement, pain control, or ovarian masses. Two patients underwent total abdominal hysterectomy-bilateral salpingo-oophorectomy for advanced disease poorly responsive to danazol therapy. In those patients desiring fertility (56), there were 38 pregnancies in 26 women, for an overall fertility rate of 46%. The overall recurrence rate was 33%, as determined by symptoms and physical findings. Significant side effects from danazol were reported by 85% of the patients. The major side effects were weight gain, edema, decrease in breast size, oily skin, hirsutism, and deepening of the voice. Only one patient discontinued danazol therapy due to side effects. Clinical tissues concerning the use of danazol with or without surgery and the miscarriage rate following danazol therapy are discussed.

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

Danazol suppression of luteinizing hormone secretion: a role for danazol-androgen receptor interaction within the brain-pituitary complex

We investigated the relationship between intracellular androgen and estrogen receptors within the brain-pituitary complex and danazol suppression of luteinizing hormone secretion in castrated rats. Danazol did not influence 3H-estradiol-estrogen receptor interactions within the brain and pituitary but did suppress 3H-dihydrotestosterone-androgen receptor interactions within this neuroendocrine complex. To study the significance of these danazol-androgen receptor interactions, the drug was administered to androgen receptor-deficient pseudohermaphrodite or flutamide-treated male rats. In both instances, danazol suppression of luteinizing hormone release was markedly attenuated or absent. These findings point to danazol-androgen receptor interactions within the brain-pituitary complex as a key step in this drug's antigonadotropic actions. Whether the active drug form is danazol itself or a metabolite is subject to further study.

Influence of LRH on gonadotrophin and testosterone levels in the foetal male rat

Gonadotrophin and testosterone levels were measured in male foetal rats at the 21st day of gestation 30 min following administration of LRH. The releasing hormone was administered by 3 different routes: subcutaneously as a single injection to the pregnant rat; subcutaneously as 12 times repeated injection to the pregnant rat from 16th-21st day of gestation; direct injection into the amniotic cavity. Three different doses of 1, 5, and 10 microgram/kg were used. The single administration to the dam was without effect. Repeated doses resulted in a significant dose-dependent elevation of mean foetal LH: 163 ng/ml in the control animals and 133,256, and 363 ng/ml in the 1, 5, and 10 microgram/kg LRH group resp. Intra animal injections significantly increased FSH and LH levels, but only those of FSH were clearly dose-dependent. A mean of 390 ng/ml in the control group was observed, with 1 microgram/kg LRH FSH was elevated to 723 ng/ml, at 5 microgram/kg to 928 and at 10 microgram/kg to 1017 ng/ml. Testosterone levels were not significantly altered. Our results demonstrate that the pituitary of foetal rats is able to respond to LRH in the same manner as adult animals.

Review: The mechanism of action of danazol, a novel steroid derivative

Danazol is being increasingly used for the treatment of a wide range of disorders, many of which appear to bear little relation to the condition for which the drug was originally marketed--endometriosis. It has been claimed that this drug acts by means of its antigonadotrophic effects on the pituitary; however, a review of the literature reveals that its efficacy in suppressing normal endometrial growth and in causing atrophy of deposits of endometrium cannot be explained solely on this basis. Recent information indicates that, besides acting at the pituitary level, a major mechanism of action may be by a direct inhibitory effect on target tissue. It is sugggested that such a mechanism would more readily account for the diverse effects of this drug in the treatment of many disorders, all of which appear to be associated with an imbalanced sensitivity of target organs to steroid hormones. A greater understanding of its mechanism of action could lead to an even wider application of this novel drug.

Danazol binding to rat androgen, glucocorticoid, progesterone, and estrogen receptors: correlation with biologic activity

Danazol was found to possess androgenic and glucocorticoid activity in rat bioassays. In contrast, danazol displayed no significant estrogenic activity. In support of these findings, danazol bound to the 8 S androgen receptor of rat prostate cytosol and to the glucocorticoid receptor of rat liver cytosol, but danazol did not bind well to the estrogen receptor of the rat uterus. Finally, danazol bound to the progesterone receptor of the rat uterus, but controversy continues as the whether danazol possesses progestational, antiprogestational, or no progestational effects.

Effects of Danazol on pituitary gonadotrophins in post-menopausal women

Multiple sampling was carried out in 4 postmenopausal women for measurement of LH and FSH before and at the end of a 1-week treatment period with Danazol (400 mg daily). A small but significant depression of FSH was found in 3 of 4 subjects, while a significant depression of LH was only seen in 1 subject. In view of the very modest gonadotrophin suppression demonstrated in these women it is possible that Danazol also exerts its profound and sometimes rapid effects through inhibition of positive oestrogen feedback and by direct actions on the ovaries and endometrium.

Antigonadotropin (danazol) in the treatment of endometriosis. Evaluation of posttreatment fertility and three-year follow-up data

Ninety-nine women who completed danazol treatment for endometriosis proved by operation were re-evaluated clinically an average of 37 months later. The recurrence of symptoms was reported by 39 per cent and pelvic findings suggestive of endometriosis were noted in 33 per cent. An average time interval between the end of treatment and the recurrence was 15 months for the entire group. However, 31 women who conceived subsequent to treatment had a much lower recurrence rate of the disease (15 per cent) and a much longer average time until the recurrence (31 months). Of 84 infertile women who desired pregnancy after treatment, 39 conceived, for a pregnancy rate of 46.4 per cent. However, when patients with absolute sterility due to other causes were excluded, the corrected pregnancy rate was 72.2 per cent. The majority of conceptions (23) occurred within the first six months after discontinuation of danazol and a total of 30 occurred within the first year. Four second- and third-trimester intrauterine fetal deaths were observed among women who conceived within the first three cycles after discontinuation of the drug.

Effects of aging on the hypothalamic-hypophyseal-gonadal axis in female rats

The failure of reproductive function in aged rats could be due to deficiencies at the level of the ovary, pituitary, hypothalamus, or higher brain centers. The classic explanation that the ovary is depleted of follicles does not receive adequate support on the basis of histologic studies of aged ovaries. Basal serum gonadotropin levels change with increasing age in female rats. Serum follicle-stimulating hormone (FSH) levels rise while serum luteinizing hormone (LH) levels fall. Likewise, the characteristic response to castration is markedly altered in aged female rats with a reduced secretion of FSH and a minimal elevation of LH. However, the pituitaires of these animals are still caapable of responding to exogenous LH-releasing hormone with a delayed LH response whose magnitude simulates that seen in younger female animals. With increasing age there is decreased pituitary and/or hypothalamic sensitivity to the feedback action of estradiol. These data are consistent with the postulation that there is an altered hypothalamic-hypophyseal function in aged rats.

Danazol therapy in hormone-sensitive mammary carcinoma

The effect of Danazol, a synthetic gonadotropin inhibitor, on two groups of Sprague-Dawley rats with dimethylbenze (a) anthracine (DMBA) induced mammary carcinoma was studied. Twenty-four (83%) of 29 control animals developed mammary tumors. Forty-four rats in one treatment group received Danazol after tumor reached 0.5 cm in diameter. Twenty-nine (66%) demonstrated tumor regression (p less than 0.005) and in 16 (36%) tumor disappeared (p less than 0.005). In a second treatment group (given Danazol daily after administration of DMBA), only seven of 50 rats (14%) developed palpable mammary carcinoma (p less than 0.0005). Danazol therapy resulted in regression of established mammary carcinoma in rats, and produced a striking inhibition of carcinogenesis in those animals treated from the time DMBA was administered. Danazol is clinically safe; studies using it in the treatment of breast cancer in women who are candidates for hormonal ablative therapy seem warranted.

Steroid modulation of electrochemically-induced gonadotropin release in the male rat

Electrochemical stimulation (ECS) of the medial preoptic area (MPOA) in the male rat produced an attenuated release of pituitary FSH and LH analogous to that induced in the female during Diestrus I and II. However, orchidectomy followed by estradiol-benzoate replacement resulted in a massive release of LH following ECS; FSH was again minimally responsive. Electrode implantation without ECS (sham control) was without effect upon either gonadotropin. Results indicate that the male rat can be provoked to a massive release of LH by ECS when an estrogen environment is provided; androgens appear to interfere. We also conclude that the MPOA connection for releasing-hormore secretion is intact in the male rat, and is sensitive to an external stimulus.

Selective inhibition by danazol of follicle stimulating hormone during the luteal phase

In each of six healthy, normally menstruating women, serum oestradiol, progesterone, basal and post luteinizing hormone releasing hormone (LHRH) gonadotrophin measurements were made during the luteal phase of a normal cycle and in a subsequent cycle in which 800 mg of danazol was given daily from the fifth day after the presumptive date of ovulation. No differences in the serum oestradiol, progesterone, or basal gonadotrophin levels were detected, but there was a selective impairment of the follicle stimulating hormone response to LHRH. The implications of these findings are discussed.