Seasonal Changes in the Immunolocalization of Steroidogenic Enzymes in the Testes of the Japanese Black Bear (Ursus thibetanus japonicus).

Komatsu, Takeshi; Tsubota, Toshio; Yamamoto, Yoshio; Atoji, Yasuro; Suzuki, Yoshitaka

doi:10.1292/jvms.59.521

Cited by 40 publications

(52 citation statements)

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“…Immunohistochemical studies by Goyal et al [7] have detected androgen receptor in the developing testis (1-19 weeks old) and excurrent ducts of the rat. 3βHSD is the predominant regulator of testosterone production in Leydig cells [12,17]. The present findings on the expression of 3βHSD show an agerelated rise in testes, which is in accordance with these earlier reports.…”

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confidence: 93%

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Immunolocalization of Steroidogenic Enzymes in the Fetal, Neonatal and Adult Testis of the Shiba Goat

et al. 2005

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“…The present study showed that P450scc, 3βHSD, P450c17 and P450arom were well localized in adult Leydig cells. In some mammals, P450arom is localized in Leydig cells, Sertoli cells and germ cells [12,24,25]. However, in rams [3], stallions [1], humans [10] and boars [4], P450arom was localized only in Leydig cells.…”

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Immunolocalization of Steroidogenic Enzymes in the Fetal, Neonatal and Adult Testis of the Shiba Goat

et al. 2005

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“…In accordance with the findings in other mammalian species [10,11,21,22], the present study detected the metabolic enzymes from cholesterol to androstenedione (P450scc, 3βHSD and P450c17) in interstitial tissue of the Japanese black bear testis. These results are also in agreement with the immunohistochemical localization of these three enzymes in the Japanese black bear testis [2,9]. This strongly suggests that androstenedione is synthesized in the interstitial tissue, probably in Leydig cells in the bear.…”

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confidence: 89%

“…Also, there are several reports at the protein level based on the immunohistochemical method in wild animals like brown bears [8], black bears [2,9], raccoon dogs [10] and deer [11]. However, there have been few reports on the gene expression of steroidogenic enzymes in the testes of wild mammals.…”

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Localization of Five Steroidogenic Enzyme mRNAs in Japanese Black Bear (Ursus thibetanus japonicus) Testes During the Mating Season by In Situ Hybridization

Iibuchi

Shimozuru

Kamine

et al. 2010

Journal of Reproduction and Development

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Abstract. The Japanese black bear (Ursus thibetanus japonicus) is a typical seasonal breeder that has a mating season in early summer. Spermatogenesis and testicular steroidogenesis are known to develop and regress annually; however, its molecular mechanism has not yet been investigated. In the present study, we clarified the mRNA sequence of 5 steroidogenic enzymes (P450scc, 3βHSD, P450c17, 17βHSD3 and P450arom) using RT-PCR and RACE methods and the localization of these gene expressions in the bear testis using an in situ hybridization technique. The amino acid sequence deduced from each mRNA sequence had high homology with the corresponding sequences of other species and possessed a motif typical of the P450 family or short chain alcohol dehydrogenase family. Expression of P450scc, 3βHSD and P450c17 mRNA in interstitial tissue indicated that conversion from cholesterol to androstenedione occurs in Leydig cells. On the other hand, the mRNA of 17βHSD3, which plays a central role in synthesizing testosterone, was detected not only in the interstitium but also inside the seminiferous tubules, along the basement membrane. P450arom mRNAs were distributed in the seminiferous tubules. These results suggest the possibility of testosterone and estradiol-17β synthesis inside the seminiferous tubules in the bear testis. We expect that the results of this study will be useful for further investigation of the molecular mechanism of steroidogenic seasonality in the bear testis. Key words: In situ hybridization, Japanese black bear, Steroidogenic enzyme, Testis (J. Reprod. Dev. 56: [236][237][238][239][240][241][242] 2010) n the majority of mammalian species, there is a seasonal variation in gonadal activity. In males, the testicular function of spermatogenesis and steroidogenesis develops before the mating season, and regression occurs when this period is over. The Japanese black bear (Ursus thibetanus japonicus), a subspecies of the Asiatic black bear living in Japan, is a typical seasonal breeder that has a mating season in early summer. The changes in the histological appearance of the testicular seminiferous tubules and the concentration of testosterone in peripheral blood have been described for some species of bears, including the Japanese black bear [1][2][3][4][5]. However, the molecular mechanisms that produce reproductive seasonality in the testis have not yet been elucidated in bears.Spermatogenesis is primarily regulated by sex steroid hormones, such as testosterone and estradiol-17β. The biosynthesis of sex steroid hormones in animal tissues is catalyzed by three forms of cytochrome P450 and two forms of hydroxysteroid dehydrogenases [6]. The cholesterol side-chain cleavage P450 enzyme (P450scc) converts cholesterol into pregnenolone as a first step. Then, 3β-hydroxysteroid dehydrogenase (3βHSD) and 17α-hydroxylase/C17-20 lyase (P450c17) convert pregnenolone into androstenedione through progesterone (Δ4 pathway) and dehydroepiandrosterone (Δ5 pathway), respectively. Subsequently, androstenedione is converted...

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“…Aromatase protein expression differs seasonally in bank vole (Clethrionomys glareolus) testes (Bilinska et al, 2000), as do testicular 3β-hydroxysteroid dehydrogenase concentrations , 2001b. ) in Japanese black bears (Ursus thibetanus japonicus) (Komatsu et al, 1997). Expression of these steroidogenic enzymes and other regulatory factors may also differ in other seasonally breeding species, affecting local apoptotic activity.…”

Section: Role Of Testosteronementioning

confidence: 99%

Mediation of seasonal testicular regression by apoptosis

Young¹

2001

Reproduction

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Seasonal rhythms in physiology and behaviour are characteristic of most temperate and boreal species (Bronson, 1989). Synchronizing energetically demanding biological functions to the most favourable time of the year enables individuals to cope with recurring stressors such as seasonal declines in food or water availability, or annual fluctuations in ambient temperature. Environmental factors such as food availability, social cues, ambient temperature and the initial predictive cue of daylength (photoperiod) can facilitate or inhibit reproductive function seasonally. These factors maintain testicular function during favourable times of the year in some species (for example, birds), and induce testicular regression or atrophy when environmental conditions are less favourable in others (for example, small mammals). Environmental factors regulate testicular function through the hypothalamic-pituitary-gonadal (HPG) axis. Photoperiod serves as the primary predictive factor in the regulation of reproductive timing in long-and short-day breeding mammals and in most bird species (Wingfield and Kenagy, 1991;Bronson and Heideman, 1994). The general long-day breeding rodent response to seasonal changes in daylength is shown (Fig. 1); however, the actual HPG response to photoperiod is distinct among different species of birds, reptiles and mammals. Supplementary cues such as food and water availability also affect reproductive function directly, serving to fine-tune the initial, general reproductive response to photoperiod (Wingfield and Kenagy, 1991). Environmental factors that stimulate or maintain reproduction promote synthesis and secretion of GnRH from the hypothalamic median eminence, and positively regulate secretion of the gonadotrophins (LH and FSH) from the anterior pituitary (Bronson and Heideman, 1994). In contrast, non-stimulatory environmental factors decrease GnRH (pulse amplitude and frequency) release, resulting in testicular atrophy, reduced spermatogenesis and diminished testosterone production from Leydig cells, the steroidogenic somatic cells in the testicular interstitium (Sinha Hikim and Swerdloff, 1999).During the transition from the breeding to the nonbreeding state, males in most seasonally breeding species undergo 40-90% atrophy in testis mass. Cells must either undergo marked reduction in size, increases in the rate of cell death, or both, to achieve the reduction in volume observed during regression. The rate of cell division may decrease in the testis during regression, indirectly contributing to seasonal atrophy; however, total testicular DNA content in rodents is reduced with non-stimulatory photoperiod exposure, indicating an increase in cell death during regression (Desjardins and Lopez, 1983). Recent studies have examined complex changes that occur in testicular cells during seasonal reproductive regression. In this review, the contribution of apoptosis, or programmed cell death, in the mediation of seasonal atrophy is discussed. Specifically, the review focuses on the interactions of gona...

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Seasonal Changes in the Immunolocalization of Steroidogenic Enzymes in the Testes of the Japanese Black Bear (Ursus thibetanus japonicus).

Cited by 40 publications

References 40 publications

Immunolocalization of Steroidogenic Enzymes in the Fetal, Neonatal and Adult Testis of the Shiba Goat

Immunolocalization of Steroidogenic Enzymes in the Fetal, Neonatal and Adult Testis of the Shiba Goat

Localization of Five Steroidogenic Enzyme mRNAs in Japanese Black Bear (Ursus thibetanus japonicus) Testes During the Mating Season by In Situ Hybridization

Mediation of seasonal testicular regression by apoptosis

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