Stewart R E, Spicer L J, Hamilton T D, Keefer B E
Department of Animal Science, Oklahoma State University, Stillwater 74078, USA.
J Anim Sci. 1995 Dec;73(12):3719-31. doi: 10.2527/1995.73123719x.
The objective of the present study was to determine the effects of IGF-I and insulin on cell proliferation, LH receptors, and basal and LH-induced progesterone and androstenedione production by bovine thecal cells. Cells from large (> or = 8mm) bovine follicles were cultured for 1 or 2 d in medium containing 10% fetal calf serum (FCS) and treated for 1 or 2 d in serum-free medium with IGF-I, insulin, and(or) LH. Treatment with 30 and 100 ng/mL of IGF-I for 1 or 2 d increased thecal cell numbers in the absence of LH regardless of whether treatments were initiated after 1 or 2 d of exposure to 10% FCS. Co-treatment with LH reduced the stimulatory effect of IGF-I on thecal cell numbers. Insulin at 10 and 100 ng/mL increased cell numbers in the presence of LH. Both IGF-I and insulin were ineffective at stimulating thecal cell progesterone or androstenedione production in the absence of LH. However, IGF-I and insulin increased (P < .05) androstenedione and progesterone production in the presence of LH. Alone, LH had little or no effect on androstenedione and progesterone production, whereas in the presence of 30 and 100 ng/mL IGF-I or 1 to 100 ng/mL insulin, LH stimulated (P < .05) androstenedione production. The stimulatory effects of IGF-I on cell proliferation and progesterone production were not detected in the presence of 100 ng/mL insulin. However, co-treatment with various doses of IGF-I and 100 ng/mL insulin further increased androstenedione production above that seen with insulin alone. In glucose-deficient medium, 25 to 75 mg/dL of glucose increased (P < .05) thecal cell proliferation, progesterone production, and androstenedione production. In the absence or presence of glucose, insulin (100 ng/mL) increased (P < .05) thecal cell proliferation, progesterone production, and androstenedione production. Treatment with 3, 10, or 100 ng/mL LH had no effect (P > .10) on the numbers of IGF-I binding sites on thecal cells but increased (P < .05) androstenedione production. Treatment with 10 and 100 ng/mL IGF-I increased (P <.01) numbers of LH/hCG binding sites. These results indicate that IGF-I and insulin may each play a significant role in thecal cell mitogenesis and LH-induced thecal cell steroidogenesis during follicular development in cattle and that glucose enhances these effects. Furthermore, the synergism between IGF-I and LH on increasing steroidogenesis does not seem to be mediated through increased binding sites for IGF-I in bovine thecal cells but rather, in part, through increased binding sites for LH.
本研究的目的是确定胰岛素样生长因子-I（IGF-I）和胰岛素对牛卵泡膜细胞增殖、促黄体生成素（LH）受体以及基础和LH诱导的孕酮和雄烯二酮生成的影响。从直径大于或等于8毫米的牛卵泡中获取细胞，在含有10%胎牛血清（FCS）的培养基中培养1或2天，然后在无血清培养基中用IGF-I、胰岛素和（或）LH处理1或2天。在不存在LH的情况下，用30和100 ng/mL的IGF-I处理1或2天可增加卵泡膜细胞数量，无论处理是在暴露于10% FCS 1或2天后开始。与LH共同处理可降低IGF-I对卵泡膜细胞数量的刺激作用。10和100 ng/mL的胰岛素在有LH存在时可增加细胞数量。在不存在LH的情况下，IGF-I和胰岛素均无法刺激卵泡膜细胞孕酮或雄烯二酮的生成。然而，在有LH存在时，IGF-I和胰岛素可增加（P <.05）雄烯二酮和孕酮的生成。单独使用时，LH对雄烯二酮和孕酮的生成几乎没有影响，而在存在30和100 ng/mL IGF-I或1至100 ng/mL胰岛素时，LH可刺激（P <.05）雄烯二酮的生成。在存在100 ng/mL胰岛素的情况下，未检测到IGF-I对细胞增殖和孕酮生成的刺激作用。然而，用不同剂量的IGF-I与100 ng/mL胰岛素共同处理可使雄烯二酮生成进一步增加，高于单独使用胰岛素时的水平。在葡萄糖缺乏的培养基中，25至75 mg/dL的葡萄糖可增加（P <.05）卵泡膜细胞增殖、孕酮生成和雄烯二酮生成。在不存在或存在葡萄糖的情况下，胰岛素（100 ng/mL）可增加（P <.05）卵泡膜细胞增殖、孕酮生成和雄烯二酮生成。用3、10或100 ng/mL LH处理对卵泡膜细胞上IGF-I结合位点的数量没有影响（P >.10），但可增加（P <.05）雄烯二酮的生成。用10和100 ng/mL IGF-I处理可增加（P <.01）LH/人绒毛膜促性腺激素（hCG）结合位点的数量。这些结果表明，IGF-I和胰岛素可能在牛卵泡发育过程中卵泡膜细胞的有丝分裂以及LH诱导的卵泡膜细胞类固醇生成中各自发挥重要作用，并且葡萄糖可增强这些作用。此外，IGF-I与LH在增加类固醇生成方面的协同作用似乎不是通过增加牛卵泡膜细胞中IGF-I的结合位点介导的，而是部分通过增加LH的结合位点介导的。
