Publications of Jacques Balthazart
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See detailSeasonal changes in some plasma hormones in pigeons from different environments.
Saarela, S.; Hissa, R.; Etches, R. et al

in Comparative Biochemistry and Physiology (1986), 84(1), 25-31

Seasonal variation in the plasma concentration of lutropin (LH), follitropin (FSH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3) and corticosterone (B) were measured in the pigeon by RIA methods ... [more ▼]

Seasonal variation in the plasma concentration of lutropin (LH), follitropin (FSH), prolactin (PRL), thyroxine (T4), triiodothyronine (T3) and corticosterone (B) were measured in the pigeon by RIA methods. Pigeons were maintained indoors under constant ambient temperature (Ta) and simulated natural daylight (LD), 12:12 L:D regimens or outdoors exposed to seasonal variations in temperature and photoperiod at Oulu, Finland. Only slight changes of gonadotropins (LH, FSH) were observed throughout the year, without any clear photosensitive or photorefractory period. In the indoor (natural LD) group, LH stayed elevated from May until October. Interdependence between the circannual hormonal fluctuation and photoperiod could not be shown, although the amplitude of FSH, T4 and T3 fluctuation of pigeons maintained in laboratory conditions were greater than that of natural LD and outdoor pigeons, whose circannual rhythms were similar. A high concentration of plasma PRL in autumn and the peak value of B in winter for all groups are thought to be correlated to lipid metabolism. Two peaks, the first in winter and the second in autumn, observed in T4 and T3 hormone profiles, may be due to molting of the pigeons. [less ▲]

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See detailSeasonal changes in some plasma hormones in pigeons: diurnal variation under natural photoperiods with constant or seasonally changing ambient temperature.
Rintamaki, H.; Hissa, R.; Etches, R. J. et al

in Comparative Biochemistry and Physiology (1986), 84(1), 33-8

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to ... [more ▼]

The diurnal variations of several plasma hormones and free fatty acids (FFA) were studied during periods in summer and winter for pigeons reared either outdoors or indoors. The latter were subjected to constant temperature and naturally varying photoperiods. A significant seasonal variation in the mean daily levels of triiodothyronine (T3), thyroxine (T4), corticosterone (B), lutropin (LH) and FFA was seen in the outdoor birds and in the T4 and B levels of indoor birds. The diurnal variation of hormone levels was generally more pronounced in winter in both groups. Cold ambient temperature significantly decreased the plasma LH level and potentiated the increasing effect of short photoperiod on plasma B level. Diurnal variation of plasma FFA level seems to be under the control of photoperiod, without any effects due to the ambient temperature. No significant correlation was found between FFA and GH concentrations. [less ▲]

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See detailComparison of monoamine concentrations in the brains of adult male and female Japanese quail.
Ottinger, M. A.; Schumacher, M.; Clarke, R. N. et al

in Poultry Science (1986), 65(7), 1413-20

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were ... [more ▼]

A fluorometric assay measuring brain tissue concentrations of norepinephrine, dopamine, and serotonin has been validated for Japanese quail. Accuracy, precision, specificity, and parallelism were determined. The sensitivity of the assays was 6 ng/tube, which allowed individual assay of 1 to 2 mg hypothalamic tissue. In Experiment 1, relatively large areas of brain from adult, reproductively active males and females were found to differ significantly in norepinephrine content in optic lobes and for dopamine in right telencephalon. A microdissection technique was used in Experiment 2 to sample small portions of hypothalamic tissue. Sex differences were observed for norepinephrine in the sections containing the lobus paraolfactorius and the preoptic, anterior, and medial hypothalamus. Differences in monoamine content were most apparent when smaller areas dissected by microdissection were analyzed. These results give evidence for sex differences in the monoamine content in specific areas of the brain. [less ▲]

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See detailA sexually dimorphic nucleus in the quail preoptic area.
Viglietti-Panzica, C.; Panzica, G. C.; Fiori, M. G. et al

in Neuroscience Letters (1986), 64(2), 129-34

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in ... [more ▼]

The cytoarchitectural analysis of the preoptic-anterior hypothalamic region of the Japanese quail reveals a sexual dimorphism in the total volume of the medial preoptic nucleus (significantly larger in males than in females). Different nuclei of the region (dorsal preopticus, suprachiasmaticus) do not show any statistically significant difference. The sex-related difference is more consistent comparing the distribution of dark volume. This last is due to a larger number of cells containing high amount of Nissl's substance in male than in female. Present findings represent the first example of sexual dimorphism in the avian hypothalamus. [less ▲]

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See detailInteraction of androgens and estrogens in the control of sexual behavior in male Japanese quail.
Balthazart, Jacques ULg; Schumacher, M.; Malacarne, G.

in Physiology & Behavior (1985), 35(2), 157-66

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone ... [more ▼]

A series of 4 experiments was performed to study the relative contribution of androgens and estrogens in the activation of sexual behavior in castrated male quail. The synthetic androgen methyltrienolone (R 1881) which is not metabolized in androgen target tissues activated sexual behavior in castrated birds and at the dose level of 0.5-1 mg/day/animal had the same potency as testosterone (T). However R 1881 was much more active than T in the induction of cloacal gland growth and activation of crowing, two typically androgen-dependent responses. This suggests that sexual behavior is not controlled by exactly the same mechanism as crowing or cloacal gland growth. In another experiment, estradiol (E2) alone activated sexual behavior but it is only at very high doses which had clear toxic effects that a significant behavioral activation could be observed. This questions the role of E2 as the physiological agent stimulating copulation in intact birds unless it is assumed that centrally administered E2 would be much more active compared to peripheral E2 which is exposed to a very intense peripheral catabolism. In the last two experiments, a clear synergism could be detected between 5 alpha-dihydrotestosterone (5 alpha-DHT) and E2 in the activation of sexual activity and doses of hormones could be defined which had almost no activity by themselves but significantly stimulated sexual behavior when given simultaneously. It was however impossible to define a hormonal treatment with T metabolites which restored behavior to its precastration level, a result very easily achieved with T treatments. Taken together, these data suggest that activation of sexual behavior in quail does not depend only on E2, nor 5 alpha-DHT nor even on their combined action. Considering that specific T receptors which probably do not bind 5 alpha-DHT are present in the brain, it would seem justified to reconsider the possible role played by T itself in the activation of behavior. [less ▲]

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See detailHormonal correlates of gonadal regression and spontaneous recovery in Japanese quail exposed to short day-lengths.
Delville, Y.; Sulon, J.; Balthazart, Jacques ULg

in Archives Internationales de Physiologie et de Biochimie (1985), 93(2), 123-33

Adult male Japanese quail were transferred from long to short days. Plasma testosterone and dihydrotestosterone quickly decreased and this endocrine response was followed by a regression of the cloacal ... [more ▼]

Adult male Japanese quail were transferred from long to short days. Plasma testosterone and dihydrotestosterone quickly decreased and this endocrine response was followed by a regression of the cloacal gland, an androgen-target organ. After about a month, a spontaneous recovery of gonadal activity was observed in some but not all birds. It was not associated with obvious shifts in the circadian system. The physiological bases of this spontaneous recovery are discussed as well as the detailed relationships between plasma testosterone and cloacal gland size. [less ▲]

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See detailOrganization and activation of behavior in quail: role of testosterone metabolism.
Balthazart, Jacques ULg; Schumacher, M.

in Journal of Experimental Zoology (The) (1984), 232(3), 595-604

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 5 beta-dihydrotestosterone (5 beta-DHT). During the embryonic life ... [more ▼]

In quail, the hypothalamus enzymatically transforms testosterone (T) into estradiol (E2), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 5 beta-dihydrotestosterone (5 beta-DHT). During the embryonic life, the 5 beta-reductase activity is very high, which probably protects the brain of males from being behaviorally demasculinized by their endogenous T. 5 beta androstanes are inactive androgens. The decrease of 5 beta reductase with age during sexual maturation corresponds to a potentiation of the effects of T as shown by experiments that compared the effects of T and 5 alpha-DHT in adult and young quail. T metabolism is also involved in the activation of male behavior in the adult. T aromatization is probably essential for behavioral activation, but nonaromatizable androgens such as methyltrienolone, and to some extent 5 alpha-DHT, can also stimulate sexual behavior in castrates. These enzymatic activities show a clear neuroanatomical localization and are sexually dimorphic. Males produce more active metabolites (E2, 5 alpha-DHT) than females, which could explain the male's greater sensitivity to T treatments. It thus appears that T metabolism is involved in the differentiation and activation of behavior in quail. [less ▲]

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See detailChanges in testosterone metabolism by the brain and cloacal gland during sexual maturation in the Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.

in Journal of Endocrinology (1984), 100(1), 13-8

Testosterone metabolism in the brain and pituitary and cloacal glands of male and female Japanese quail was studied in vitro during sexual maturation (from 1 day to 5 weeks after hatching). The production ... [more ▼]

Testosterone metabolism in the brain and pituitary and cloacal glands of male and female Japanese quail was studied in vitro during sexual maturation (from 1 day to 5 weeks after hatching). The production of 5 alpha-dihydrotestosterone in the hyperstriatum and cloacal gland and that of androstenedione in the cloacal gland of males was highest at 1 day after hatching, which could be related to the peak of plasma androgens previously demonstrated in neonatal quail. 5 beta-Reductase activity was very high in the brain, but not the pituitary or cloacal glands of young chicks and decreased markedly, especially in the hypothalamus, during sexual maturation. As 5 beta-reduced metabolites of testosterone are inactive androgens, it is suggested that the decrease of 5 beta-reductase activity with age corresponds to a potentiation of the effects of testosterone at the level of the brain. [less ▲]

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See detailSexual dimorphism in the hypothalamic metabolism of testosterone in the Japanese Quail (Coturnix coturnix japonica).
Schumacher, M.; Balthazart, Jacques ULg

in Progress in Brain Research (1984), 61

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See detailThe postnatal demasculinization of sexual behavior in the Japanese quail (Coturnix coturnix japonica).
Schumacher, M.; Balthazart, Jacques ULg

in Hormones and Behavior (1984), 18(3), 298-312

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds ... [more ▼]

Three experiments were performed to analyze the time course of demasculinization in the Japanese quail and to test the activating and organizing effects of estradiol (E2) in adult sexually active birds. In Experiment 1, males and females were castrated at the age of 1 day or 1, 2, 4, and 6 weeks and treated as adults with testosterone (T). The age of castration had no effect on behavior and morphology in males. Plasma gonadotrophins (LH and FSH) were, however, higher in males castrated at or before than in those castrated after 2 weeks of age. This suggests that postnatal testicular secretions have organizing effects on the pituitary activity. Females which were castrated before 1 week of age were less sensitive to the activating effects of T than males, but were not fully demasculinized. The demasculinization of different reproductive characteristics such as male sexual behavior, cloacal gland size, and weight of the syringeal muscles is achieved in females at different times posthatching. In Experiment 2, castration of male and female quail at the ages of 4 days or 4 weeks confirmed that postnatal ovarian secretions contribute to the full behavioral and morphological demasculinization of females. It is easier to elicit mounting in T-treated females when they are tested in their home cage instead of a test arena. This difference was not observed in males. During Experiment 3, it was impossible to demasculinize sexually active adult males or females by treatment with Silastic implants of E2. E2 did not maintain sexual behavior in ovariectomized females showing male sexual behavior when treated with T but maintained the behavior in males. [less ▲]

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See detailEstradiol contributes to the postnatal demasculinization of female Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.

in Hormones and Behavior (1984), 18(3), 287-97

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization ... [more ▼]

Two experiments were performed to characterize the process of postnatal demasculinization in Japanese quail. In the first experiment, it was shown that estradiol (E2) can complete female demasculinization during the first 4 weeks of life. By contrast, E2 did not demasculinize sexual behavior and cloacal gland in neonatally castrated males. Neonatally gonadectomized females preferentially performed mount attempts when tested in their home cage by comparison to a test arena. In Experiment 2, E2 Silastic implants (40-mm) maintained full copulatory behavior in castrated males but not in females. This large dose of E2 did not demasculinize adult sexually active birds (males or females) even if treatment lasted for 1 month. It is concluded that E2 can demasculinize sexual behavior only in females and only if treatment is performed in very young birds. [less ▲]

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See detailAltered brain metabolism of testosterone is correlated with reproductive decline in aging quail.
Balthazart, Jacques ULg; Turek, R.; Ottinger, M. A.

in Hormones and Behavior (1984), 18(3), 330-45

In aging quail, an increasing proportion of males show no sexual behavior. A decrease in the mean size of the tests, cloacal gland, and sternotracheal muscles is also observed. In both sexually active and ... [more ▼]

In aging quail, an increasing proportion of males show no sexual behavior. A decrease in the mean size of the tests, cloacal gland, and sternotracheal muscles is also observed. In both sexually active and inactive males, plasma testosterone decreases with age but more so in inactive birds. The behavioral and morphological changes observed during aging are correlated with shifts in the intracellular testosterone metabolism resulting in a change in the ratio of active versus inactive metabolites. In the hypothalamus there is a steady decrease with age of 5 beta-reductase activity in all birds and an increase in 5 alpha-reductase activity only in the birds which remain sexually active. In the cloacal gland, the 5 beta-reductase activity markedly increases with age but more so in the birds which become sexually inactive. These data support the notion that the effects of testosterone are controlled by enzymatic shifts which could modulate the sensitivity to the hormone at the cellular level. [less ▲]

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See detailPartial characterization of testosterone-metabolizing enzymes in the quail brain.
Schumacher, M.; Contenti, E.; Balthazart, Jacques ULg

in Brain Research (1984), 305(1), 51-9

The properties of 5 beta-reductase, 5 alpha-reductase and aromatase, 3 testosterone metabolizing enzymes, were studied in the quail brain by an in vitro incubation technique. The results describe the ... [more ▼]

The properties of 5 beta-reductase, 5 alpha-reductase and aromatase, 3 testosterone metabolizing enzymes, were studied in the quail brain by an in vitro incubation technique. The results describe the changes in time of metabolite production and the effects of temperature, enzyme and cofactor concentrations. The apparent Km and Vmax were evaluated for the 3 enzymes. Aromatase and 5 alpha-reductase have a higher affinity but a lower capacity than 5 beta-reductase. The kinetics of the latter enzyme are complex and suggest the presence of two types of enzymes. These characteristics fit in well with the role probably played by the enzymes in vivo. [less ▲]

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See detailRelative potencies of testosterone and 5 alpha-dihydrotestosterone on crowing and cloacal gland growth in the Japanese quail (Coturnix coturnix japonica).
Balthazart, Jacques ULg; Schumacher, M.; Malacarne, G.

in Journal of Endocrinology (1984), 100(1), 19-23

It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5 beta-reductase in the young ... [more ▼]

It has been suggested that testosterone is less effective at inducing crowing behaviour in young birds than in adults because of the presence of higher levels of steroid 5 beta-reductase in the young brain, which converts testosterone to inactive 5 beta-reduced metabolites. This hypothesis was tested indirectly by comparing the relative potencies of 5 alpha-dihydrotestosterone (5 alpha-DHT), which cannot be converted to 5 beta-metabolites, and testosterone at inducing crowing in young gonadectomized male and female quail. The promotion of cloacal gland growth by these treatments was also assessed since there are no age-related changes in 5 beta-reductase in this organ. Silicone elastomer implants (2 X 5, 5 and 10 mm) containing 5 alpha-DHT were more effective at stimulating crowing than similar implants of testosterone whilst there was little difference in their potency at inducing cloacal gland growth. These results are consistent with the hypothesis that brain steroid 5 beta-reductase regulates the behavioural activity of testosterone in the brain of young birds. [less ▲]

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See detailEffect of the presence of females on the pituitary-testicular activity in male Japanese quail (Coturnix coturnix japonica).
Delville, Y.; Sulon, J.; Hendrick, J. C. et al

in General and Comparative Endocrinology (1984), 55(2), 295-305

Five experiments were carried out to study the role of the presence of a female on the reproductive endocrinology of male Japanese quail. In the first three experiments, exposure of an adult male raised ... [more ▼]

Five experiments were carried out to study the role of the presence of a female on the reproductive endocrinology of male Japanese quail. In the first three experiments, exposure of an adult male raised in long days to a female for l0 min or l week failed to increase plasma testosterone and LH levels; in fact a significant transitory decrease in plasma testosterone was observed, associated with a preceding increase in plasma corticosterone. These changes are interpreted as a result of the stress caused by repeated bleeding or by the continuous presence of a female in a limited space. In the last two experiments, an increase in the maturation rate of immature males could be observed in birds maintained in the continuous presence of females by comparison with birds kept in isolation. The paired males had larger cloacal glands and testes and higher plasma levels of testosterone and LH than the isolated one. This effect of the female was observed in long days (l6L:8D) as well as in marginally stimulating short days (l2L:l2D). [less ▲]

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See detailThe effect of pinealectomy on plasma levels of gonadotrophins and growth hormone in the pigeon (Columba livia).
Rintamaki, H.; Hissa, R.; Balthazart, Jacques ULg et al

in Journal of Pineal Research (1984), 1(4), 381-9

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See detailTestosterone metabolism and testosterone-dependent characteristics in Japanese quail.
Delville, Y.; Hendrick, J. C.; Sulon, J. et al

in Physiology & Behavior (1984), 33(5), 817-23

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 ... [more ▼]

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 intracellular 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 production of 5 beta-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. [less ▲]

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See detailThe effects of testosterone and its metabolites on sexual behavior and morphology in male and female Japanese quail.
Schumacher, M.; Balthazart, Jacques ULg

in Physiology & Behavior (1983), 30(3), 335-9

Adult Japanese quail are sexually dimorphic. Even when implanted with testosterone (T), ovariectomized females fail to copulate and their cloacal glands are smaller than those of males. This may be due to ... [more ▼]

Adult Japanese quail are sexually dimorphic. Even when implanted with testosterone (T), ovariectomized females fail to copulate and their cloacal glands are smaller than those of males. This may be due to a reduced capacity of the females to transform testosterone into active metabolites (estradiol-17 beta and 5 alpha-dihydrotestosterone). Indeed, in the male quail, estradiol-17 beta (E2) activates copulation whereas 5 alpha-dihydrotestosterone (5 alpha-DHT) activates crowing, strutting and the development of the cloacal gland. To test this hypothesis, we studied the effects of in vivo treatments of male and female quail with the different T-metabolites. Forty-one castrated male and female quail were implanted with subcutaneous silastic implants of T, 5 alpha-DHT, E2 and E2 in combination with 5 alpha-DHT. When implanted with these metabolites, females failed to copulate and their cloacal glands remained less developed than those of males. Sexual differences in behavior and morphology thus cannot be entirely explained by sexual dimorphism of the metabolism. [less ▲]

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See detailTestosterone metabolism in discrete areas of the hypothalamus and adjacent brain regions of male and female Japanese quail (Coturnix coturnix Japonica).
Schumacher, M.; Contenti, E.; Balthazart, Jacques ULg

in Brain Research (1983), 278(1-2), 337-40

The metabolism of testosterone in small regions of the hypothalamus was studied by an in vitro radioenzymatic assay in male and female Japanese quail. 5 beta-reduction was the most important metabolic ... [more ▼]

The metabolism of testosterone in small regions of the hypothalamus was studied by an in vitro radioenzymatic assay in male and female Japanese quail. 5 beta-reduction was the most important metabolic pathway. This enzymatic activity is not evenly distributed in the brain: it shows a rostral to caudal decrease. There is some suggestion that 5 beta-reduction could be more active in females than in males which could contribute to the behavioral dimorphism in this species. [less ▲]

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See detailSexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone.
Balthazart, Jacques ULg; Schumacher, M.; Ottinger, M. A.

in General and Comparative Endocrinology (1983), 51(2), 191-207

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first ... [more ▼]

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males. [less ▲]

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