Age-related Changes of Reproductive Hormones in Young Meishan Boars

Kanematsu, Nobue; Wei, Jin; Watanabe, Gen; Taya, Kazuyoshi

doi:10.1262/jrd.18013

Cited by 15 publications

(15 citation statements)

References 19 publications

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“…This type of relationship between inhibin and testosterone is also seen in land mammals and it has been reported that the circulating inhibin levels in male cattle were high prior to sexual maturity compared with levels after sexual maturity [8,13]. Although the exact mechanism of inhibin decrease and testosterone increase after sexual maturity is not known, it could be due to suppression of gonadotropin-releasing hormone secretion in the hypothalamus by the high testosterone concentration.…”

Section: Discussionmentioning

confidence: 77%

Circulating Testosterone and Inhibin Levels at Different Ages in the Male Beluga (Delphinapterus leucas)

Katsumata

Ueda

Arai

et al. 2012

The Journal of Veterinary Medical Science

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ABSTRACT. This study is the first report on circulating testosterone and inhibin levels in a species of whales, the beluga. Circulating testosterone and immunoreactive (ir-) inhibin levels in two captive male belugas ("Nack", originally from Canada and "Duke", from the Okhotsk Sea) were measured every month for 9 years between 1995 and 2003. Assuming that clearly increased testosterone levels in the circulation indicates that the belugas had reached sexual maturity, at the ages of 10 ("Nack") and 11 years old ("Duke"). Their testosterone levels before the significant increase (pre-pubertal) were 0.42  0.07 ng/ml (n=18) and 0.35  0.10 ng/ml (n=18) and, those of after the increase (maturity) were 1.65  0.14 ng/ml (n=74) and 2.06  0.14 ng/ml (n=74). Circulating ir-inhibin levels before sexual maturity were 0.78  0.04 ng/ml (n=18) and 0.64  0.04 ng/ml (n=15) and, after sexual maturity were 0.52  0.02 ng/ml (n=56) and 0.43  0.02 ng/ml (n=67). Seasonal changes were observed in the testosterone levels after sexual maturity and the levels increased during March and April in Canadian origin "Nack", and peaked in February in Okhotsk origin "Duke". Circulating ir-inhibin level gradually decreased as they aged. A negative correlation between the circulating testosterone and ir-inhibin was observed. No seasonal changes were observed in the ir-inhibin levels after sexual maturity. These data will surely correspond to clarification of endocrinology and the successful reproduction of the beluga.

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Section: Discussionmentioning

confidence: 77%

Circulating Testosterone and Inhibin Levels at Different Ages in the Male Beluga (Delphinapterus leucas)

Katsumata

Ueda

Arai

et al. 2012

The Journal of Veterinary Medical Science

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“…In previous studies on circulating inhibin, FSH, LH and testosterone levels in relation to age in bull calves [ 7 , 8 , 9 , 18 ], pigs [ 10 , 22 ] and horses [ 2 , 3 ] it was reported that circulating inhibin concentration is higher in the sexually immature stage than the mature stage. Similarly, it was reported that the circulating inhibin level is remarkably high in calves, until they reach sexual maturation [ 17 ].…”

Section: Discussionmentioning

confidence: 99%

Circulating gonadotropins and testicular hormones during sexual maturation and annual changes in male bottlenose dolphins (Tursiops truncatus)

Katsumata¹,

Jaroenporn

Ueda

et al. 2017

The Journal of Veterinary Medical Science

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To reveal the reproductive biology in male bottlenose dolphins (Tursiops truncatus), circulating gonadotropins (follicle stimulating hormone [FSH] and luteinizing hormone [LH]) and testicular hormones (testosterone and inhibin) were monitored for 8−12 years in 2 captive bottlenose dolphins (Mars and Regulus). During the study period, Mars was undergoing sexual maturation, whereas Regulus was already mature at the beginning of the study. Assuming that Mars had reached sexual maturity when the significant increase in circulating testosterone levels was observed, serum concentration of inhibin was higher in the sexually immature stage than in the mature stage, whereas the serum concentration of FSH was higher in the sexually mature stage than in the immature stage. No difference was observed in the LH levels between pre- and post-sexual maturation. There was a significant increase in serum concentration of testosterone during spring in both animals. These results suggest that the mechanism responsible for regulating FSH secretion by inhibin functions during the sexually immature stage in this species.

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“…However, Meishan boars undergo pubertal testicular development at a much younger age than Piau boars. Growth of seminiferous tubules to a mean diameter of 100 m occurs before 50 d of age in Meishan boars [17][18][19], but the seminiferous tubules of Piau boars do not achieve this diameter until after 120 d of age [20,21], and the size of postpubertal testes of Piau boars is greater than in Meishan boars. Furthermore, our second study provided no support for a correlation of testicular diameter early in pubertal development with testicular size of adult boars.…”

Section: Discussionmentioning

confidence: 99%

Assessment of pubertal development of boars derived from ultrasonographic determination of testicular diameter

Ford

Wise

2011

Theriogenology

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At the onset of puberty, seminiferous tubules rapidly increase in diameter, thereby occupying a greater proportion of the testis, resulting in a rapid increase in testicular size. The objective of the current studies was to evaluate ultrasonography for assessing testicular diameter, as a basis for ranking boars relative to their extent of pubertal development. In the initial study, prior to castration at 4, 5, 6, or 7 mo of age, testicular length and diameter were assessed by ultrasonography in 160 anesthetized boars. After castration, testes were weighed. Mean diameter of seminiferous tubules and percentage of the testis occupied by tubules were determined by histological evaluations of all testes. Testicular volume was calculated from length and diameter and was correlated with testicular weight (P < 0.001; r ≧ 0.78) within each of the four age groups. At 4 and 5 mo of age, testicular diameter correlated positively (P < 0.001) with diameter of seminiferous tubules; this relationship was not significant at older ages. In two subsequent studies, testicular diameter determined ultrasonographically in conscious boars was highly correlated (r > 0.8) when assessed twice on the same day, or when diameter of the right was compared with diameter of the left testis. Similarly, testicular diameter obtained initially at 92 d of age correlated positively (P < 0.001) with the diameter observed at older ages, but the magnitude of the relationship decreased as time between evaluations increased. These findings supported ultrasonographic determination of testicular diameter during early pubertal development, as a means to rank boars of similar chronological age for extent of pubertal development.

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Age-related Changes of Reproductive Hormones in Young Meishan Boars

Cited by 15 publications

References 19 publications

Circulating Testosterone and Inhibin Levels at Different Ages in the Male Beluga (<i>Delphinapterus leucas</i>)

Circulating Testosterone and Inhibin Levels at Different Ages in the Male Beluga (<i>Delphinapterus leucas</i>)

Circulating gonadotropins and testicular hormones during sexual maturation and annual changes in male bottlenose dolphins (<i>Tursiops truncatus</i>)

Assessment of pubertal development of boars derived from ultrasonographic determination of testicular diameter

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