卵巣内卵胞の発育と血漿中ステロイドホルモンおよび性腺刺激ホルモンに及ぼす組換型ブタインヒビンαサブユニットのポニー種雌馬への受動免疫の効果 Effect of Active Immunization of Pony Mares against Recombinant Porcine Inhibinα Subunit on Ovarian Follicular Development and Plasma Steroids and Gonadotropins

2頭のポニー種雌馬に対して39日間隔で3回組換型ブタインヒビンαサブユニットで免疫した。血中のインヒビン抗体価は初回免疫後27日に有意(P<0.05)に上昇した。結合活性の最高値は第2回目の追加免疫後12日に到達した。免疫後の小および中,大卵胞数は免疫前のそれに比べて有意に増大した(11.75±4.30,2.75±0.69,2.51±0.63 vs 6.50±1.43,1.83±0.44,1.33±0.38)。しかし,排卵率は免疫後も変わらなかった。発情周期中の血漿中FSHおよびエストラジオール17β濃度は免疫後有意(P<0.05)に増加した。今回の結果から,インヒビンに対する免疫はポニー種雌馬において発情周期中の卵胞数を増大するための有効な手法と思われた。さらに,インヒビンがステロイドホルモンと協調してFSH分泌に対する抑制的な効果を介して卵胞の発育調整に重要な役割を果たすとする概念を支持するものであった。

Two pony mares were immunized against recombinant porcine inhibin α subunit three times with 39 day intervals. Clinical findings and endocrinological changes before immunization were taken as the control. The first significant rise in the anti-inhibin titre (P<0.05) in the circulation was found 27 days after the first injection. Maximum binding activity was reached by the 12th day after the second booster dose. The number of small, medium and large sized follicles had increased significantly compared to before immunization (11.75 ± 4.30, 2.75 ± 0.69 and 2.51 ± 0.63 vs 6.50 ± 1.43, 1.83 ± 0.44 and 1.33 ± 0.38, respectively), but the ovulation rate remained unchanged after immunization. The average plasma concentration of FSH and estradiol-17β during the estrous cycle increased significantly (P<0.05) after immunization. These results suggest that immunization against inhibin is a useful tool to increase the number of ovarian follicles during the estrous cycle of pony mares. Moreover, the present stuc[y supported the concept that inhibin plays a major role in the control of follicular growth through its inhibitory effect on FSH secretion synergistically with steroid hormones.