Gong J G, Baxter G, Bramley T A, Webb R
Roslin Institute (Edinburgh), Midlothian, UK.
J Reprod Fertil. 1997 May;110(1):91-7. doi: 10.1530/jrf.0.1100091.
Treatment with recombinant bovine somatotrophin (bST) can enhance the development of ovarian antral follicles in cattle. The underlying mechanism was examined further by performing a dose-response study to investigate the effects of bST on peripheral concentrations of somatotrophin, insulin-like growth factor I (IGF-I), insulin, FSH and LH, and ovarian follicle development. Twenty mature heifers were randomly divided into five groups and injected s.c. at 6 h intervals for 7 days with 25% of one of the following daily doses of bST: 0, 3.13, 6.25, 12.5 or 25.0 mg. Ovarian follicular dynamics were monitored by real-time ultrasonography. Blood samples were collected daily during the experiment, and every 15 min for 8 h on days 1 and 5 of bST treatment. Treatment with bST increased (P < 0.01) peripheral concentrations of somatotrophin in a dose-dependent manner. Serum concentrations of both IGF-I and insulin were significantly (P < 0.01) increased in all heifers given 12.5 or 25.0 mg bST per day. Peripheral concentrations of IGF-I and insulin in all animals in the group given 3.13 mg bST and two heifers in the group given 6.25 mg bST were not different from those in the control group, while concentrations in the other two heifers given 6.25 mg bST were significantly (P < 0.01) higher. The number of ovarian follicles < 5 mm in diameter was increased (P < 0.05) in response to bST, but only in heifers (n = 10) with significantly increased serum concentrations of IGF-I and insulin. There were no effects of treatment on peripheral concentrations of FSH, LH and progesterone, and on the numbers of follicles > 5 mm in diameter. In conclusion, this study has demonstrated in vivo that the effect of treatment with bST on ovarian follicle development appears to be mediated through an increase in circulating IGF-I or insulin concentrations, rather than via an alteration in the secretion of pituitary gonadotrophins or a direct effect of bST on ovarian follicles.
用重组牛生长激素（bST）进行治疗可促进牛卵巢窦状卵泡的发育。通过进行剂量反应研究进一步探究其潜在机制，以研究bST对生长激素、胰岛素样生长因子I（IGF-I）、胰岛素、促卵泡素（FSH）和促黄体素（LH）外周浓度以及卵巢卵泡发育的影响。将20头成年小母牛随机分为五组，每隔6小时皮下注射一次，持续7天，注射以下每日剂量bST中的一种的25%：0、3.13、6.25、12.5或25.0毫克。通过实时超声检查监测卵巢卵泡动态。实验期间每天采集血样，在bST治疗的第1天和第5天，每15分钟采集一次，共采集8小时。bST治疗使外周生长激素浓度呈剂量依赖性增加（P < 0.01）。每天给予12.5或25.0毫克bST的所有小母牛血清IGF-I和胰岛素浓度均显著增加（P < 0.01）。给予3.13毫克bST组的所有动物以及给予6.25毫克bST组的两头小母牛外周IGF-I和胰岛素浓度与对照组无差异，而给予6.25毫克bST的另外两头小母牛的浓度显著更高（P < 0.01）。对bST有反应的情况下，直径<5毫米的卵巢卵泡数量增加（P < 0.05），但仅在血清IGF-I和胰岛素浓度显著增加的小母牛（n = 10）中出现这种情况。治疗对FSH、LH和孕酮的外周浓度以及直径>5毫米的卵泡数量没有影响。总之，本研究在体内证明，bST治疗对卵巢卵泡发育的作用似乎是通过循环中IGF-I或胰岛素浓度的增加介导的，而不是通过垂体促性腺激素分泌的改变或bST对卵巢卵泡的直接作用。
