Department of Animal and Range Sciences, South Dakota State University, 1039 N Campus Dr., Brookings, SD 57007, USA.
Domest Anim Endocrinol. 2011 Feb;40(2):67-76. doi: 10.1016/j.domaniend.2010.09.001. Epub 2010 Oct 14.
Components of the circulating and anterior pituitary insulin-like growth factor (IGF) system vary in response to steroids in pigs. However, whether serum and anterior pituitary concentrations of the IGF system vary throughout the estrous cycle has not been determined. To further examine this relationship, estrus was synchronized in 40 gilts of similar age and weight (180 d; 120 kg) by feeding 15 mg altrenogest for 15 d to synchronize estrus. Gilts were checked twice daily for expression of estrus beginning 3 d after the end of altrenogest treatment and continuing for 7 d. The first day each gilt exhibited estrus was designated as day 1 of the estrous cycle. Blood samples were obtained by jugular venipuncture on days 1, 4, 7, 10, 13, 16, 19, and 22 of the estrous cycle. On days 7, 13, 19, and 22 of the estrous cycle 10 pigs were killed and anterior pituitary glands (AP) were collected. Serum concentrations of IGF-I and AP concentrations of IGF-I were determined by radioimmunoassay. Relative amounts of AP IGF binding protein (IGFBP) were determined by western ligand blot analysis. Relative expression of AP IGF-I, IGF-I receptor (IGF-I-R), gonadotropin-releasing hormone receptor (GnRHR), and luteinizing hormone (LH)-β subunit were determined by real-time reverse transcription polymerase chain reaction. Serum concentrations of IGF-I fluctuated throughout the estrous cycle. Mean serum concentrations of IGF-I decreased (P < 0.02) from day 1 through day 10, increased (P < 0.02) on days 13 through 16, and then decreased (P < 0.02) from days 19 through 22. Mean AP concentrations of IGF-I were greater (P < 0.03) on day 19 than on all other days, whereas no difference was detected (P > 0.05) in mean AP concentrations of IGF-I on days 7, 13, and 22. Mean relative amounts of AP IGFBP-2 and -5 were each greater (P < 0.02) in gilts on day 19 than on all other days, whereas no difference was detected (P > 0.05) in mean relative amounts of AP IGFBP-2 and -5 among pigs on days 7, 13, and 22 of the estrous cycle. Relative expression AP IGF-I was greater (P < 0.05) on days 13, 19, and 22 than on day 7 of the estrous cycle. Similarly, the relative expression of AP IGF-IR was increased (P < 0.05) in gilts on days 13, 19, and 22 compared with day 7. The relative expression of GnRHR was greater (P < 0.05) on days 13 and 22 of the estrous cycle than on day 7. The relative expression of LHβ subunit was greater (P < 0.05) on day 19 of the estrous cycle than on days 7, 13, and 22. Anterior pituitary release of LH throughout the porcine estrous cycle may be modulated by changes in the intrapituitary IGF system.
循环系统和前垂体胰岛素样生长因子（IGF）系统的成分会对猪体内的类固醇产生反应。然而，IGF 系统在发情周期中血清和前垂体的浓度是否发生变化还没有确定。为了进一步研究这种关系，用 15mg 阿尔特龙格斯特（altrenogest）给 40 头体重和年龄相似（180 日龄；120 公斤）的小母猪同步发情，15 天为一个周期。在阿尔特龙格斯特处理结束后 3 天开始，每天两次检查小母猪的发情表现，持续 7 天。小母猪首次发情的第一天被指定为发情周期的第 1 天。发情周期的第 1、4、7、10、13、16、19 和 22 天通过颈静脉采血。在发情周期的第 7、13、19 和 22 天，10 头母猪被杀死并采集前垂体（AP）。用放射免疫法测定血清 IGF-I 浓度和 AP IGF-I 浓度。用 Western 配体印迹分析测定 AP IGF 结合蛋白（IGFBP）的相对含量。用实时逆转录聚合酶链反应（RT-PCR）测定 AP IGF-I、IGF-I 受体（IGF-IR）、促性腺激素释放激素受体（GnRHR）和黄体生成素（LH）-β亚基的相对表达。血清 IGF-I 浓度在发情周期中波动。血清 IGF-I 浓度从第 1 天到第 10 天降低（P <0.02），从第 13 天到第 16 天增加（P <0.02），然后从第 19 天到第 22 天再次降低（P <0.02）。AP IGF-I 浓度在第 19 天高于其他所有天数（P <0.03），而在第 7、13 和 22 天，AP IGF-I 浓度没有差异（P >0.05）。AP IGFBP-2 和 -5 的相对含量在第 19 天的小母猪中均高于其他所有天数（P <0.02），而在第 7、13 和 22 天的小母猪中，AP IGFBP-2 和 -5 的相对含量没有差异（P >0.05）。AP IGF-I 的相对表达在发情周期的第 13、19 和 22 天高于第 7 天（P <0.05）。同样，AP IGF-IR 的相对表达在发情周期的第 13、19 和 22 天也高于第 7 天（P <0.05）。GnRHR 的相对表达在发情周期的第 13 和 22 天高于第 7 天（P <0.05）。LHβ亚基的相对表达在发情周期的第 19 天高于第 7、13 和 22 天（P <0.05）。猪发情周期中 LH 的前垂体释放可能受到垂体内 IGF 系统变化的调节。
