Le Gac F, Loir M, le Bail P Y, Ollitrault M
Institut National de la Recherche Agronomique, Laboratoire de Physiologie des Poissons, Rennes, France.
Mol Reprod Dev. 1996 May;44(1):23-35. doi: 10.1002/(SICI)1098-2795(199605)44:1<23::AID-MRD3>3.0.CO;2-V.
Few data exist concerning the occurrence and potential role of an insulin-like growth factor (IGF) system in fish gonads. Using Northern and slot blot hybridization with a specific salmon IGF-I cDNA, we confirmed that IGF-I transcription occurs in trout testis. Testicular IGF-I mRNA abundance may be increased by long-term GH treatment in juvenile fish, while shorter treatment with growth hormone (GH) or a gonadotropin (GTH-II) in maturing males had no statistically significant effect. Radiolabelled recombinant human IGF-I binds with high affinity to crude trout testis preparation, to cultured isolated testicular cells, and to a membrane fraction of these cells (Ka = 0.2 to 0.7 x 10(10) M-1; Bmax = 10 to 20 fmol/10(7) cells, and 68 fmol/mg protein of membrane). The binding site was identified as type 1 IGF receptor by its binding specificity (IGF-I > IGF-II >>> insulin) and the molecular size of its alpha-subunit labelled with 125I-IGF-I (M(r)125-140 kDa). 125I-IGF-II also bound to the type 1 receptor whereas IGF-II/ mannose 6 phosphate receptors could not be detected. Separation of isolated testicular cells by Percoll gradient and centrifugal elutriation provided populations enriched in different types of intratubular cells. IGF-I mRNA (detected by reverse transcription + polymerase chain reaction [PCR]) and IGF-I receptors (measured by competitive binding) were observed to a greater extent in Sertoli cell-enriched populations and in spermatogonia with primary spermatocytes. Therefore, IGF-I is a potential paracrine/autocrine regulator inside the spermatogenic compartment and appears as a possible mediator of GH action at the gonadal level in fish.
关于胰岛素样生长因子（IGF）系统在鱼类性腺中的发生情况及潜在作用，现有的数据很少。我们使用与特定鲑鱼IGF-I cDNA的Northern和狭缝印迹杂交技术，证实了IGF-I转录发生在虹鳟睾丸中。幼鱼长期接受生长激素（GH）治疗可能会增加睾丸中IGF-I mRNA的丰度，而成熟雄鱼短期接受生长激素（GH）或促性腺激素（GTH-II）治疗则无统计学上的显著影响。放射性标记的重组人IGF-I与虹鳟睾丸粗提物、培养的分离睾丸细胞及其细胞膜部分具有高亲和力结合（Ka = 0.2至0.7×10(10) M-1；Bmax = 10至20 fmol/10(7) 细胞，以及68 fmol/mg膜蛋白）。通过其结合特异性（IGF-I > IGF-II >>> 胰岛素）及其α亚基与125I-IGF-I标记后的分子大小（M(r)125 - 140 kDa），确定该结合位点为1型IGF受体。125I-IGF-II也与1型受体结合，而未检测到IGF-II/甘露糖6磷酸受体。通过Percoll梯度和离心淘洗分离分离的睾丸细胞，得到了富含不同类型管内细胞的群体。在富含支持细胞的群体以及精原细胞与初级精母细胞中，观察到了更多的IGF-I mRNA（通过逆转录 + 聚合酶链反应[PCR]检测）和IGF-I受体（通过竞争性结合测量）。因此，IGF-I是生精区室内潜在的旁分泌/自分泌调节因子，并且似乎是鱼类性腺水平上GH作用的可能介质。
