Méndez E, Smith A, Figueiredo-Garutti M L, Planas J V, Navarro I, Gutiérrez J
Departament de Fisiologia, Facultat de Biologia, D. III, Universitat de Barcelona, Avinguda Diagonal 645, Barcelona, 08028, Spain.
Gen Comp Endocrinol. 2001 May;122(2):148-57. doi: 10.1006/gcen.2001.7621.
Insulin and IGF-I binding has been studied in brown trout (Salmo trutta) wheat germ agglutinin semipurified receptors from embryos (organogenesis), larvae (yolk sac), juveniles (2.98 +/- 0.21 g bw) and adults (111.6 +/- 6.92 and 522 +/- 53 g bw). Embryos and larvae were sampled at 5 and 12 weeks after fertilization (December 1999 and February 2000) and juvenile and adults were taken simultaneously (July 1999) and under the same feeding conditions to minimize potential nutritional and seasonal effects. Insulin receptor number was maximal at 12 weeks (144 fmol/mg glycoprotein) and progressively decreased in subsequent samplings. No alterations in affinity were detected (K(d) range, 0.21-0.32 nM) and changes in number of receptor paralleled changes in total specific binding. IGF-I receptor number was highest at 5 weeks (1044 fmol/mg) and was significantly higher than values for insulin in all samplings. The affinity of IGF-I receptor did not change (K(d) range, 0.11-0.18 nM) but was consistently higher than that for the insulin receptor. A more rapid decrease of IGF-I binding and receptor number was found with age. However, the ratio of insulin/IGF-I binding established in 12-week-old larvae (0.18 +/- 0.01) was thereafter maintained at very similar values in juveniles and adults (0.15-0.17). Tyrosine kinase activity (TKA) for insulin receptors ranged between 136 and 183% and there were no significant changes with age. For the IGF-I receptor, TKA ranged from 174 to 281% and was significantly higher in 5-week-old larvae coincident with the highest levels of receptor number and declined gradually in parallel with binding levels. In conclusion, the greater abundance of IGF-I receptors during embryonic and larval development is maintained throughout juvenile and adult stages. This would suggest a key role for IGF-I in the growth and metabolism of trout muscle.
已对褐鳟（Salmo trutta）胚胎（器官形成期）、幼体（卵黄囊期）、幼鱼（体重2.98±0.21克）和成鱼（体重111.6±6.92克和522±53克）的小麦胚芽凝集素半纯化受体中的胰岛素和胰岛素样生长因子-I（IGF-I）结合情况进行了研究。胚胎和幼体在受精后5周和12周（1999年12月和2000年2月）取样，幼鱼和成鱼在同一时间（1999年7月）且在相同饲养条件下获取，以尽量减少潜在的营养和季节影响。胰岛素受体数量在12周时达到最大值（144飞摩尔/毫克糖蛋白），并在随后的取样中逐渐减少。未检测到亲和力的改变（解离常数（K(d)）范围为0.21 - 0.32纳摩尔），受体数量的变化与总特异性结合的变化平行。IGF-I受体数量在5周时最高（1044飞摩尔/毫克），且在所有取样中均显著高于胰岛素受体的值。IGF-I受体的亲和力没有变化（K(d)范围为0.11 - 0.18纳摩尔），但始终高于胰岛素受体的亲和力。随着年龄增长，发现IGF-I结合和受体数量下降得更快。然而，12周龄幼体中建立的胰岛素/IGF-I结合比率（0.18±0.01）在幼鱼和成鱼中此后维持在非常相似的值（0.15 - 0.17）。胰岛素受体的酪氨酸激酶活性（TKA）在136%至183%之间，且随年龄无显著变化。对于IGF-I受体，TKA范围为174%至281%，在5周龄幼体中显著更高，与受体数量的最高水平一致，并与结合水平平行逐渐下降。总之，在胚胎和幼体发育过程中IGF-I受体的丰度更高，在幼鱼和成鱼阶段都得以维持。这表明IGF-I在鳟鱼肌肉的生长和代谢中起关键作用。
