片側精巣を摘出した黒毛和種雄子牛における残存精巣の内分泌学的および組織学的解析
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This study examined plasma testosterone (T) levels before and after a human chorionic gonadotropin (hCG) injection and the histological findings of the excised testes from control (intact), hemicastrated and bilaterally castrated Japanese Black calves. In Experiment 1, the first hCG stimulation test (IM 14 or 28) was conducted in 19 calves. They were hemicastrated on 7 days after the hCG injection and divided into two groups, and the second hCG stimulation test was conducted on 14 days after hemicastration in one group (HC 14) or 28 days after hemicastration in the other group (HC 28). The remaining testes were removed in all calves on 7 days after the second hCG injection, and the third hCG stimulation test was conducted at 14 days after bilaterally castrated (BC 14 or 28). Plasma T levels were investigated just before (day 0) , on 5 (day 5) and 7 days (day 7) after each hCG injection. In Experiment 2, 12 calves aged 237 ± 7 days old were used, and the testes excised from control (n=4) and hemicastrated calves in HC 14 (n=4) and HC 28 (n=4) groups were examined histologically. Plasma T levels at day 0 in IM and HC groups were significantly higher than BC group, whereas there was no significant difference between IM and HC groups. In IM and HC groups expect HC 28 group, plasma T levels after the hCG injection were significantly higher than before. HC 28 group showed significantly the higher area ratio of seminiferous tubules and the lower Sertoli cell counts in seminiferous tubules than control calves. In conclusion, although plasma T levels on 14 days after hemicastration were equivalent to control calves, compensatory changes in the remaining testes were not observed histologically after hemicastration.試験的に片側精巣を摘出した子牛を作出し,血中テストステロン(T)濃度,人絨毛性性腺刺激ホルモン(hCG)に対する反応性を正常,片側精巣,去勢時で比較し,片側精巣の摘出による残存させた精巣の組織学的な変化を調べた. 試験1として,正常雄子牛(IM 14群,IM 28群),右側精巣のみを摘出した後14日(HC14群)か28日(HC28群)の牛,その後残存させていた左側精巣を摘出した後14日の牛(BC14群,BC28群)に,hCG負荷試験としてhCG投与直前(day0),hCG3,000IU投与後5日,7日(day5,7)に採血を行い,血中T濃度を測定した. 試験2として,試験1の供試牛のうち残存させた左側精巣を摘出した日齢が237±7日だった8頭(HC14群:4頭,HC28群:4頭)を供し,237± 7日齢で両側精巣を同時に摘出したControl群(n=4)と,摘出した左側精巣の組織学的変化を比較した. その結果,試験1においてday0の血中T濃度はIM群,HC群間で有意な差はみられず,BC群は他の2群と比べて有意に低かった(p<0.01). IM群はhCG投与後有意に上昇しその後有意に下降した(P<0.05). 試験2において,HC28群はControl群よりも,精細管領域率が有意に高く(P<0.05),10本あたり精細管内セルトリ細胞数が有意に少なかった(p<0.05)が,ライディッヒ細胞数に有意な差はみられなかった. 片側精巣を摘出後14日以上経過した牛は,残存させた精巣のみで正常雄子牛の血中T濃度と同等のレベルを維持し,この変化は残存させた片側精巣の組織学的な変化によらないことがわかった.
- 2012-02-24
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