Okano Tsukasa, Murase Tetsuma, Tsubota Toshio
United Graduate School of Veterinary Medicine, Gifu University.
J Vet Med Sci. 2003 Oct;65(10):1093-9. doi: 10.1292/jvms.65.1093.
Twenty-one wild male Japanese black bears (Ursus thibetanus japonicus) were captured in the summer-autumn of 1998-2000 in the vicinity of Neo Village, Gifu Prefecture. Testes were measured, and testicular samples were biopsied and observed histologically. Four steroidogenic enzymes, i.e., cholesterol side-chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase (3betaHSD), 17-alpha hydroxylase cytochrome P450 (P450c17), and aromatase cytochrome P450 (P450arom) were immunolocalized. Serum testosterone concentrations were measured by radioimmunoassay. Testis size changed little from 1-3 years of age, increased rapidly at 4 years, and attained its peak at 5 years. Serum testosterone concentrations ranged from 0.05 to 1.78 ng/m l, and the mean +/- standard deviation was 0.43 +/- 0.48 ng/ml. Age of sexual maturation in wild male Japanese black bears was estimated to be 3-4 years. Seasonal changes in spermatogenesis were obvious; active in June, July and August, degenerated by September. Leydig cells, Sertoli cells and germ cells have the capability of synthesizing androgen, and Leydig cells, Sertoli cells, spermatids and spermatogonia have the capability of synthesizing estrogen in Japanese black bears.
1998年至2000年夏秋季节，在岐阜县根尾村附近捕获了21只野生雄性日本黑熊（Ursus thibetanus japonicus）。测量了睾丸大小，并对睾丸样本进行活检和组织学观察。对四种类固醇生成酶，即胆固醇侧链裂解细胞色素P450（P450scc）、3β-羟基类固醇脱氢酶（3βHSD）、17-α羟化酶细胞色素P450（P450c17）和芳香化酶细胞色素P450（P450arom）进行了免疫定位。通过放射免疫测定法测量血清睾酮浓度。睾丸大小在1至3岁时变化不大，4岁时迅速增加，并在5岁时达到峰值。血清睾酮浓度范围为0.05至1.78 ng/ml，平均值±标准差为0.43±0.48 ng/ml。野生雄性日本黑熊的性成熟年龄估计为3至4岁。精子发生的季节性变化明显；6月、7月和8月活跃，9月退化。在日本黑熊中，睾丸间质细胞、支持细胞和生殖细胞具有合成雄激素的能力，而睾丸间质细胞、支持细胞、精子细胞和精原细胞具有合成雌激素的能力。
