Raper S, Kothary P, Ishoo E, Dikin M, Kokudo N, Hashimoto M, DeMatteo R P
Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia 19104-4268, USA.
Regul Pept. 1995 Jul 21;58(1-2):55-62. doi: 10.1016/0167-0115(95)00058-j.
Insulin-like growth factors I and II are peptides with a structural homology for proinsulin, and are involved in hepatocyte proliferation. IGF-I and IGF-II, however, have different metabolic roles, and their mechanisms of action are incompletely known. We hypothesized that IGF-I and IGF-II act by different signal transduction pathways. To test this hypothesis, hepatocytes from 200 g male Sprague-Dawley rats were isolated by a two-step collagenase perfusion technique and plated at a density of 10(5) cells/16 mm Primaria plate. Proliferation was measured by [3H]thymidine ([3H]thy) incorporation into DNA, and an autoradiographic nuclear labeling index (LI). To analyze signal transduction, cyclic AMP (cAMP) levels were measured 5 min after addition of reagents by a radioimmunoassay. Reagents (doses) used were: IGF-I (2 nM), IGF-II (2 nM), the inhibitory peptide somatostatin-14 (SS14) (10 nM), and the adenylyl cyclase antagonist dideoxyadenosine (DDA) (10 microM). A summary of the findings is as follows: (1) IGF-I stimulates [3H]thy, LI and cAMP accumulation. (2) IGF-II stimulates [3H]thy and LI but not cAMP; (3) IGF-I but not IGF-II effects are inhibited by SS14 and DDA. We conclude that the hepatotrophic effects of IGF-I and IGF-II occur by different mechanisms: IGF-I is cAMP-dependent, IGF-II is cAMP-independent.
胰岛素样生长因子I和II是与胰岛素原具有结构同源性的肽，并且参与肝细胞增殖。然而，IGF-I和IGF-II具有不同的代谢作用，其作用机制尚不完全清楚。我们推测IGF-I和IGF-II通过不同的信号转导途径发挥作用。为了验证这一假设，采用两步胶原酶灌注技术从200 g雄性Sprague-Dawley大鼠分离肝细胞，并以10(5)个细胞/16 mm Primaria培养板的密度接种。通过将[3H]胸腺嘧啶核苷([3H]thy)掺入DNA以及放射自显影核标记指数(LI)来测量增殖。为了分析信号转导，在加入试剂5分钟后通过放射免疫测定法测量环磷酸腺苷(cAMP)水平。所用试剂(剂量)如下：IGF-I(2 nM)、IGF-II(2 nM)、抑制性肽生长抑素-14(SS14)(10 nM)以及腺苷酸环化酶拮抗剂双脱氧腺苷(DDA)(10 microM)。研究结果总结如下：(1)IGF-I刺激[3H]thy、LI和cAMP积累。(2)IGF-II刺激[3H]thy和LI，但不刺激cAMP；(3)IGF-I而非IGF-II的作用受到SS14和DDA的抑制。我们得出结论，IGF-I和IGF-II的肝细胞营养作用通过不同机制发生：IGF-I是cAMP依赖性的，IGF-II是cAMP非依赖性的。
