Sexual differences in the Japanese quail: Behavior, morphology, and intracellular metabolism of testosterone (original) (raw)
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Brain Research, 1987
An in vitro radioenzymatic assay and purification procedure by thin-layer chromatography were used to study the metabolism of dihydrotestosterone (DHT) into 3a-and 3fl-androstanediols by the brain and cloacai gland of Japanese quail. Kinetic studies showed that these 2 metabolites are produced in a linear fashion with respect to time of incubation for up to 15 min but that they continue to accumulate for up to 4 h. The maximum velocity of these reactions is high (nmol/mg protein/15 min), but the affinities of the enzymes for DHT are low (in the/~M range). The enzymatic activities are not evenly distributed in the brain: they are high in the tuberal hypothalamus and iobus parolfactorius but low in the preoptic area and anterior hypothalamus. Enzyme activities are not markedly affected by treatment of the birds with either testosterone or DHT. The activity of these enzymes is lower in the preoptic area and tuberal hypothalamus of DHT-treated birds which display female-directed sexual behavior than in the same brain areas of birds which are sexually inactive. We discuss the relationships between this reductive metabolism of DHT and the activational effects of the steroid on sexual behavior.
Testosterone metabolism and testosterone-dependent characteristics in Japanese quail
Physiology & Behavior, 1984
In 2 independent experiments, we measured and correlated in maturing male Japanese quail the individual variations in sexual and aggressive behavior, cloacal gland size, testes weight, plasma testosterone concentrations and intraceilular testosterone metabolism by hypothalamus and cloacal gland. Cloacal gland area was only weakly related to plasma testosterone levels but was positively correlated with the production of active androgenic metabolites and negatively related to the producition of 5/3-reduced androgens (inactive) in the glandular tissue. Several measures of behavior were correlated with aspects of the testosterone metabolism in the anterior hypothalamus. In both experiments, the behavior of the birds was also strongly correlated with their testes weight and their cloacal gland area but weakly or not at all with their plasma testosterone levels. These studies suggest that testosterone metabolism is involved in the control of hormone action in maturing animals.
Neuroanatomical distribution of testosterone-metabolizing enzymes in the Japanese quail
Brain Research, 1987
We describe a very sensitive and precise assay which allows one to study the metabolism of testosterone (T) in small brain nuclei dissected out according to the method of Palkovits and Brownstein. With this method, the neuroanatomical distributions of aromatase, and 5a-and 5fl-reductase activities were studied in adult male quail (Coturnix coturnix japonica). The different enzymes show different neuroanatomical distributions. Production of estradiol-17fl (E2) was highest in the sexually dimorphic nucleus preopticus medialis (POM). We showed previously that the preoptic aromatase activity is higher in male than in female quail. As the POM is a central and very large structure within the preoptic area, the present results suggest a relationship between the neuroanatomical and the biochemical sex differences. By contrast, the production of 5a-DHT was highest in the lateral hypothalamic area (LHY), the bed nucleus of the pallial commissure (BPC) and the lateral septum (SL). The 5fl-reductase activity was highest in the lateral septum and in the ventral part of the archistriatum (AV). Moreover, there was a rostral to caudal decrease in 5fl-reductase activity in the hypothalamus.
Sex Differences in the Expression of Sex Steroid Receptor mRNA in the Quail Brain
Journal of Neuroendocrinology, 2009
In Japanese quail, males will readily exhibit the full sequence of male-typical sexual behaviors but females never show this response even after ovariectomy and treatment with male-typical concentrations of exogenous testosterone. Testosterone aromatization plays a key-limiting role in the activation of this behavior but the higher aromatase activity in the brain of males compared to females is not sufficient to explain the behavioral sex difference. The cellular and molecular bases of this prominent sex difference in the functional consequences of testosterone have not been identified so far. We hypothesized that the differential expression of sex steroid receptors in specific brain areas could mediate this behavioral sex difference and therefore quantified by radioactive in situ hybridization histochemistry the expression of the mRNA coding for the androgen receptor (AR) and the estrogen receptors (ER) of the α and β sub-types. All three receptors were expressed in an anatomically discrete manner in various nuclei of the hypothalamus and limbic system and, at usually lower densities, in a few other brain areas. In both sexes, the intensity of the hybridization signal for all steroid receptors was highest in the medial preoptic nucleus (POM), a major site of testosterone action related to the activation of male sexual behavior. Although no sex difference in the optical density of the AR hybridization signal could be found in POM, the area covered by AR mRNA was significantly larger in males than in females, indicating a higher overall degree of AR expression in this region in males. In contrast, females tended to have significantly higher levels of AR expression than males in the lateral septum. ERα was more densely expressed in females than males throughout the medial preoptic and hypothalamic areas (including the POM and the medio-basal hypothalamus [MBH)], an area implicated in the control of female receptivity) and in the mesencephalic nucleus intercollicularis. ERβ was more densely expressed in the medio-basal hypothalamus of females but a difference in the reverse direction (males>females) was observed in the nucleus taeniae of the amygdala. These data suggest that a differential expression of steroid receptors in specific brain areas could mediate at least certain aspects of the sex differences in behavioral responses to testosterone but they do not appear to be sufficient to explain the complete lack of activation by testosterone of maletypical copulatory behavior in females.
Sex Differences in the Metabolic Effects of Testosterone in Sheep
Endocrinology, 2012
Adiposity is regulated in a sexually divergent manner. This is partly due to sex steroids, but the differential effects of androgens in males and females are unclear. We investigated effects of testosterone on energy balance in castrated male (n = 6) and female sheep (n = 4), which received 3 × 200 mg testosterone implants for 2 wk or blank implants (controls). Temperature probes were implanted into retroperitoneal fat and skeletal muscle. Blood samples were taken to measure metabolites and insulin. In males, muscle and fat biopsies were collected to measure uncoupling protein (UCP) mRNA and phosphorylation of AMP-activated protein kinase and Akt. Testosterone did not change food intake in either sex. Temperature in muscle was higher in males than females, and testosterone reduced heat production in males only. In fat, however, temperature was higher in the castrate males compared with females, and there was no effect of testosterone treatment in either sex. Preprandial glucose leve...
The transformation of testosterone into dihydrotestosterone by the brain and the anterior pituitary
Journal of Steroid Biochemistry, 1972
Slices of rat pituitary gland, hypothalamus, amygdala, cerebral cortex and prostate have been incubated in vitro with labelled testosterone; the metabolites formed have been identified. Testosterone is converted into l7/3-hydroxy-So-androstan-3-one (androstanolone, dihydro testosterone, DHT) by all tissues examined. The prostate is the structure which effects such a conversion to the greatest extent; the pituitary gland and the hypothalamus are also very active; the cerebral cortex and the amygdala are also able to transform testosterone into DHT, but the rate of conversion is not as great as that found in the tissues previously mentioned. Androstenedione. 5a-androstan-3,17-dione and So-androstan-3a, 17/3-diol are also formed by some of the tissues. Castration increases and treatment with exogenous testosterone decreases the transformation of testosterone into DHT at the pituitary and the hypothalamic level. Both at the hypothalamic and the pituitary level, the addition in vitro of progesterone, 1 l-deoxycorticosterone. I I-deoxycortisol and corticosterone reduces the transformation of testosterone into DHT; on the contrary, the addition of pituitary FSH increases the conversion of testosterone into its 'active' metabolite. The ability to transform testosterone into DHT is much higher in all structures examined (with the exception of the prostate) in prepuberal than in adult rats.
Effects of sex steroids on aromatase mRNA expression in the male and female quail brain
General and Comparative Endocrinology, 2011
Castrated male quail display intense male-typical copulatory behavior in response to exogenous testosterone but ovariectomized females do not. The behavior of males is largely mediated by the central aromatization of testosterone into estradiol. The lack of behavioral response in females could result from a lower rate of aromatization. This is probably not the case because although the enzymatic sex difference is clearly present in gonadally intact sexually mature birds, it is not reliably found in gonadectomized birds treated with testosterone, in which the behavioral sex difference is always observed. We previously discovered that the higher aromatase activity in sexually mature males as compared to females is not associated with major differences in aromatase mRNA density. A reverse sex difference (females > males) was even detected in the bed nucleus of the stria terminalis. We analyzed here by in situ hybridization histochemistry the density of aromatase mRNA in gonadectomized male and female quail that were or were not exposed to a steroid profile typical of their sex. Testosterone and ovarian steroids (presumably estradiol) increased aromatase mRNA concentration in males and females respectively but mRNA density was similar in both sexes. A reverse sex difference in aromatase mRNA density (females >males) was detected in the bed nucleus of subjects exposed to sex steroids. Together these data suggest that although the induction of aromatase activity by testosterone corresponds to an increased transcription of the enzyme, the sex difference in enzymatic activity results largely from post-transcriptional controls that remain to be identified.
The Role of Androgen Metabolism in the Activation of Male Behavior
Annals of the New York Academy of Sciences, 1986
Although we have begun to realize the importance of hormone metabolism in modulating an individual's response to particular gonadal hormones, the full import of normal metabolic influences still escapes us. For many years, scientists interested in endocrine function in the male focused primarily on the production of testosterone (T). T metabolism was viewed primarily as a catabolic process, resulting in the breakdown of the active hormone and its excretion. A large number of androgenic metabolites were identified, but most of them were ignored because they had minimal biological potency when their activity was assessed in various bioassay systems such as rat seminal vesicle or chick comb. One exception to this was 5a-dihydrotestosterone (DHT). First, DHT was shown to be more potent than testosterone in several bioassay systems, and then in the sixties, conclusive evidence was published which documented the local formation of DHT in male sexual accessory tissues. These findings sparked research on the importance of local metabolism in increasing, as well as decreasing, the biological activity of gonadal hormones. Research on the formation and mechanism of action of DHT in the sexual accessory tissues proved invaluable in developing a general model of androgen metabolism and action. The higher concentrations and more uniform distribution of hormones and hormone receptors in peripheral tissues allowed researchers to carry out studies on these tissues which were not technically or practically feasible in brain tissue. Ironically, the focus on sexual accessory tissues led many to ignore metabolic pathways other than Sa-reduction, but when scientists began to study the role of androgen metabolism in the activation of behavior, it became obvious that other metabolic pathways were also important, since DHT showed limited effectiveness in activating normal levels of male social behavior. This pointed to the importance of another metabolic process, the aromatization of androgens to estrogens, for estrogenic metabolites play an important role in activating male behaviors in many species. This research has highlighted the possibility that many behaviors which have been described as androgen dependent will prove in fact to be dependent on estrogens formed from androgenic precursors. Aromatization and 5a-reduction are opposing metabolic pathways. That is, once an androgen is Sa-reduced, most evidence suggests that it can no longer be converted