Maestro M A, Méndez E, Párrizas M, Gutiérrez J
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain.
Biol Reprod. 1997 May;56(5):1126-32. doi: 10.1095/biolreprod56.5.1126.
Insulin and insulin-like growth factor-I (IGF-I) receptors were characterized in glycoprotein fractions prepared by wheat germ agglutinin-agarose affinity chromatography from the ovaries of carp. Insulin-specific overall binding in carp ovaries was 6- to 11-fold lower than IGF-I binding (2.7 +/- 0.48% vs. 22.8 +/- 3.6% per 20 microg glycoprotein). Cold IGF-I displaced radiolabeled IGF-I binding in doses 1000- to 3000-fold lower than cold insulin. On the other hand, cold insulin displaced radiolabeled insulin binding at concentrations 5- to 30-fold lower than cold IGF-I. The alpha-subunit molecular masses of carp insulin and IGF-I receptors were smaller than the alpha-subunit molecular mass of rat insulin receptor (125 and 120 vs. 135 kDa, respectively). Autophosphorylation of carp beta-subunit insulin and IGF-I receptors showed similar molecular masses that did not differ from the molecular mass of rat insulin beta subunit. Receptor tyrosine kinase activity was stimulated in a dose-dependent manner by insulin and IGF-I. Insulin and IGF-I stimulated tyrosine kinase activity and reached a maximum, respectively, of 224 +/- 14% and 279 +/- 7% of basal phosphorylation. Insulin and IGF-I binding characteristics were measured through different stages of follicular development. High specific binding of both peptides in primary oocyte growth (5.6 +/- 0.8% and 50 +/- 10% per 20 microg glycoprotein for insulin and IGF-I, respectively) decreased to a minimum at the end of vitellogenesis, followed by a slight increase later, in the preovulatory stage. The presence of insulin and IGF-I receptors in carp ovaries and the changes in percentage of binding throughout the reproductive cycle suggest that, in carp, the roles of insulin and IGF-I depend on the ovarian maturation stage.
通过麦胚凝集素-琼脂糖亲和层析从鲤鱼卵巢制备的糖蛋白组分中对胰岛素和胰岛素样生长因子-I（IGF-I）受体进行了表征。鲤鱼卵巢中胰岛素特异性总结合比IGF-I结合低6至11倍（每20微克糖蛋白分别为2.7±0.48%和22.8±3.6%）。冷IGF-I以比冷胰岛素低1000至3000倍的剂量取代放射性标记的IGF-I结合。另一方面，冷胰岛素以比冷IGF-I低5至30倍的浓度取代放射性标记的胰岛素结合。鲤鱼胰岛素和IGF-I受体的α亚基分子量小于大鼠胰岛素受体的α亚基分子量（分别为125和120 kDa，而大鼠胰岛素受体为135 kDa）。鲤鱼β亚基胰岛素和IGF-I受体的自磷酸化显示出相似的分子量，与大鼠胰岛素β亚基的分子量没有差异。胰岛素和IGF-I以剂量依赖性方式刺激受体酪氨酸激酶活性。胰岛素和IGF-I刺激酪氨酸激酶活性，分别达到基础磷酸化的224±14%和279±7%的最大值。通过卵泡发育的不同阶段测量胰岛素和IGF-I的结合特性。在初级卵母细胞生长阶段，两种肽的高特异性结合（胰岛素和IGF-I每20微克糖蛋白分别为5.6±0.8%和50±10%）在卵黄发生结束时降至最低，随后在排卵前期略有增加。鲤鱼卵巢中胰岛素和IGF-I受体的存在以及整个生殖周期中结合百分比的变化表明，在鲤鱼中，胰岛素和IGF-I的作用取决于卵巢成熟阶段。
