黒毛和種牛の初回卵胞波の交代と組織内分泌学的観察 Dynamics and Histological Observation of First Follicular Wave in Japanese Black Cows

黒毛和種牛の初回卵胞波の交代と,事前に主席卵胞(DF)と最大次席卵胞(SF)を確認した卵巣を発情周期の7日(3頭)と10日(3頭) (発情日=d0)に摘出し,卵胞の免疫組織学的所見を観察した。初回卵胞波を1日2回超音波診断法により観察し,卵胞数やDFとSFの直径を求め,摘出卵胞の顯粒層細胞(GC)と卵胞膜細胞(TC)のアポトーシス割合をTunel法で検索した。卵胞波の発現時,クラス1の卵胞(直径2-5mm)13.5±9.5個が排卵後12時間で見られ,卵胞数はd1の午後まで増加した。DFとSFの直径は卵胞波発現時には4.9±0.8mm,4.9±0.9mmであった。DFとSFの逸脱は,d3の午後に起こり,その際の直径は8.9±1.3mm,6.8±0.9mmであった。DFはd8の午後まで発育し,直径は14.4±1.8mm(n=3)で,その後閉鎖した。DFの卵胞壁はd7には健康な組織所見を示し,d10にはやや閉鎖していたが,SFはd7とd10には重度の閉鎖像を示していた。アポトーシス細胞の割合は,DFはd7とd10のGCでは4.4±1.0%,17.9±4.9%であり,同日のTCでは2.4±0.7%,8.0±1.4%であった。今回の結果から,1)牛の初回卵胞波ではクラス1卵胞の24時間以内のリクルート,DFとSFの逸脱が見られ,2)DFの退行では重度のアポトーシス発現の先行することが明らかとなった。

Aims: To determine the turnover of the first follicular wave in Japanese black cows and quantitative immunohistological characteristics of the previously in vivo identified dominant follicle (DF) and largest subordinate follicle (SF) derived from ovariectomy on Day 7 (3 cows) and Day 10 (3 cows) (Day 0=estrus). Six cases of first follicular wave in cows were observed twice daily by ultrasound scanning. The number of follicles, diameter of DF and SF, and prevalence of apoptotic granulosa cells (GC) and theca cells (TC) were studied by TUNEL methods. At follicular wave emergence, 13.5±9.5 Class I (2-5 mm in diameter follicles) were found 12 hr after ovulation, and increased its number until Day 1 pm. Future DE and SF observed retrospectively were 4.9±0.8 mm and 4.9±0.9 mm at wave emergence. Deviation of DF and SF occurred on Day 3 pm with mean diameters of 8.9±1.3 mm and 6.8±0.9 mm, respectively. DF developed until Day 8 am with a maximum diameter of 14.4±1.8 mm (n=3) and then regressed. The follicular wall of the DF had a characteristic image of a healthy follicle on Day 7 and slightly atretic DF on Day 10, whereas SF showed heavy atresia on both Day 7 and Day 10 under HE staining. In the prevalence of apoptotic cells, DF were 4.4±1.0% and 17.9±4.9% on Day 7 and on Day l0 in GC, respectively, and 2.4±0.7% and 8.0±1.4% on Day 7 and on Day l0 in TC, respectively. These results showed that, 1) the first follicular wave in cows is characterized by 24 hr recruitment of small follicles and a gradual divergence of growth rates in future DF and SF, and 2) early regression of DF on Day 10 was preceded by severe apoptosls.