Ge Z, Nicholson W E, Plotner D M, Farin C E, Gadsby J E
Department of Anatomy, Physiological Sciences and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27695, USA.
J Reprod Fertil. 2000 Sep;120(1):109-14.
Insulin-like growth factor I (IGF-I) is believed to play a luteotrophic role in the pig corpus luteum during the oestrous cycle. Since the actions of IGF-I in target tissues are mediated by the type I IGF receptor, the concentrations of IGF-I receptor mRNA and protein were examined in pig corpora lutea at different stages of the oestrous cycle. Corpora lutea were collected from normally cyclic gilts on days 4, 7, 10, 13, 15 and 16 of the oestrous cycle (n = 4 animals per day). Corpora lutea on days 7, 10 and 13 were dissociated with collagenase, and large and small luteal cell sub-populations were separated by elutriation. Northern and slot blots were used to examine mRNA, and western blots were used to measure the concentrations of IGF-I receptor protein in the pig corpus luteum. On northern blots, luteal IGF-I receptor mRNA was present as a single 11 kb transcript. The slot blots showed that the steady state expression of IGF-I receptor mRNA increased significantly (P < 0.05) from its lowest value on day 4, to reach a maximum on days 13-16. IGF-I receptor mRNA was also expressed to a greater extent in large compared with small luteal cells (P < 0.05). On western blots, IGF-I receptor appeared as a 95 kDa protein band (beta-subunit) and IGF-I receptor protein concentrations were significantly higher (P < 0.05) on days 4-10 than on days 13-16. Finally, large luteal cells appeared to contain more IGF-I receptor protein than the small luteal cells. In conclusion, since IGF-I receptor was detected in the pig corpus luteum, it is a likely target tissue for IGF-I, especially during the early luteal phase. Furthermore, IGF-I receptor was localized primarily on large luteal cells, thus it is hypothesized that IGF-I may play a paracrine role in the pig corpus luteum.
胰岛素样生长因子I（IGF-I）被认为在母猪发情周期中对黄体起促黄体作用。由于IGF-I在靶组织中的作用是由I型IGF受体介导的，因此研究了发情周期不同阶段猪黄体中IGF-I受体mRNA和蛋白的浓度。在发情周期的第4、7、10、13、15和16天从正常发情的后备母猪收集黄体（每天n = 4只动物）。用胶原酶解离第7、10和13天的黄体，并通过淘析分离大、小黄体细胞亚群。用Northern印迹和狭缝印迹检测mRNA，用Western印迹测量猪黄体中IGF-I受体蛋白的浓度。在Northern印迹上，黄体IGF-I受体mRNA以单一的11 kb转录本形式存在。狭缝印迹显示，IGF-I受体mRNA的稳态表达从第4天的最低值显著增加（P < 0.05），在第13 - 16天达到最大值。与小黄体细胞相比，大黄体细胞中IGF-I受体mRNA的表达也更高（P < 0.05）。在Western印迹上，IGF-I受体表现为一条95 kDa的蛋白带（β亚基），IGF-I受体蛋白浓度在第4 - 10天显著高于第13 - 16天（P < 0.05）。最后，大黄体细胞似乎比小黄体细胞含有更多的IGF-I受体蛋白。总之，由于在猪黄体中检测到了IGF-I受体，它可能是IGF-I的靶组织，尤其是在黄体早期。此外，IGF-I受体主要定位于大黄体细胞，因此推测IGF-I可能在猪黄体中发挥旁分泌作用。
