Echternkamp S E, Spicer L J, Gregory K E, Canning S F, Hammond J M
United States Department of Agriculture, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933.
Biol Reprod. 1990 Jul;43(1):8-14. doi: 10.1095/biolreprod43.1.8.
Recent studies have implicated insulin-like growth factor I (IGF-I) as an intraovarian regulator of follicular growth and differentiation. Therefore, we investigated the possibility that cattle selected for twin births may have increased concentrations of IGF-I within the ovarian follicle and(or) in peripheral blood. The estrous cycles of 14 cows with histories of producing twins and 12 control monotocous cows were synchronized with 35 mg of prostaglandin F2 alpha (PGF2 alpha). Blood and follicular fluid were collected 48-50 h post-administration of PGF2 alpha (follicular phase of the estrous cycle). Concentrations of IGF-I were measured by RIA after acid-ethanol treatment of serum or follicular fluid. Twin-producing cows had a greater (p less than 0.05) number of large (greater than or equal to 4 mm) follicles and 47% greater (p less than 0.05) concentrations of IGF-I in peripheral blood than control cows. Cattle selected for high twinning frequency also had greater (p less than 0.05) concentrations of IGF-I (+/- SE) in the two largest follicles than control (unselected) cows (327 +/- 28 vs. 243 +/- 29 ng/ml). IGF-I concentrations in pooled small (1-3.9 mm) follicles were less (p less than 0.05) than in large follicles but did not differ between control and twin-producing cattle. In addition, the percentage of IGF-I concentrations measured in follicular fluid to that of serum was lower (p less than 0.05) in small follicles than in large follicles, and was greater (p less than 0.05) in large follicles of control (93.2 +/- 5.3%) than twin-producing (76.2 +/- 4.4%) cattle.(ABSTRACT TRUNCATED AT 250 WORDS)
近期研究表明，胰岛素样生长因子I（IGF-I）是卵泡生长和分化的卵巢内调节因子。因此，我们研究了选择双胎出生的母牛卵巢卵泡内和（或）外周血中IGF-I浓度可能升高的可能性。对14头有双胎生产史的母牛和12头对照单胎母牛的发情周期，用35毫克前列腺素F2α（PGF2α）进行同步化处理。在给予PGF2α后48 - 50小时（发情周期的卵泡期）采集血液和卵泡液。血清或卵泡液经酸乙醇处理后，用放射免疫分析法（RIA）测定IGF-I浓度。与对照母牛相比，双胎生产母牛的大卵泡（直径大于或等于4毫米）数量更多（p < 0.05），外周血中IGF-I浓度高47%（p < 0.05）。选择高双胎率的母牛，其两个最大卵泡中的IGF-I浓度（±标准误）也高于对照（未选择）母牛（327 ± 28对243 ± 29纳克/毫升，p < 0.05）。合并的小卵泡（1 - 3.9毫米）中IGF-I浓度低于大卵泡（p < 0.05），但对照母牛和双胎生产母牛之间无差异。此外，小卵泡中卵泡液与血清中IGF-I浓度的百分比低于大卵泡（p < 0.05），对照母牛大卵泡中的该百分比（93.2 ± 5.3%）高于双胎生产母牛（76.2 ± 4.4%，p < 0.05）。（摘要截断于250字）
