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

Journal of Veterinary Medical Science

Toshio TSUBOTA²  Takeshi KOMATSU¹  Yasuro ATOJI³  Yoshio YAMAMOTO³  Yoshitaka SUZUKI³ 

[1] United Graduate School of Veterinary Science, Faculty of Agriculture, Gifu University;Laboratories of Theriogenology, Faculty of Agriculture, Gifu University;Veterinary Anatomy, Faculty of Agriculture, Gifu University

关键词: bear testis;    seasonal change;    spermatogenesis;    steroidogenic enzyme;    testosterone;   

DOI  :  10.1292/jvms.59.521

学科分类：兽医学

来源: Japanese Society of Veterinary Science

【 摘 要 】

References(43)Cited-By(24)Seasonal changes in sites of immunostaining of steroidogenic enzymes were examined in testes of the Japanese black bear, Ursus thibetanus japonicus. In addition, serum concentrations of testosterone and estradiol-17β were investigated by radioimmunoassay, and the seasonal changes were compared with the results of immunostaining. On the basis of morphological observations of spermatogenic activity, the reproductive cycle was divided into five periods: an active period in May and June; a degenerative period in November; a resting period in January; an early-resumptive period in March; and a late-resumptive period in April. Serum concentrations of testosterone differed with season accompanied by differences in spermatogenic activity, with baseline levels in November and January, increasing levels in March and April, and high levels in May, and April and June of the next year. Immunoreactivities specific for cholesterol side-chain cleaving cytochrome P450, 17α-hydroxylase cytochrome P450 and 3β-hydroxysteroid dehydrogenase (3βHSD) were observed in Leydig cells throughout the year. Only the percentages of Leydig cells immunopositive for 3βHSD exhibited seasonal differences that correlated with serum concentrations of testosterone. Aromatase cytochrome P450 (P450arom) was immunolocalized in Leydig and Sertoli cells throughout the year, in spermatids in May, and April and June of the next year and in myoid cells in January and March. The percentages of Leydig cells immunopositive for this enzyme increased in May, and January, March and June of the next year. On the other hand, no pattern of seasonal change in serum estradiol-17β concentration was observed. These results suggest that 3βHSD is a key enzyme in the regulation of the testosterone production in Leydig cells. Furthermore, estrogen derived from Leydig and myoid cells seems to play a role in the regulation of Leydig cells by negative feedback as a paracrine and/or autocrine mediator.

【 授权许可】

Unknown