Baxter R C
Kolling Institute of Medical Research, Royal North Shore Hospital, Sydney, Australia.
Horm Res. 1994;42(4-5):140-4. doi: 10.1159/000184186.
The actions and bioavailability of the insulin-like growth factors (IGFs) are regulated by a family of six IGF binding proteins. IGFBP-3, the major circulating IGFBP, is unique in combining with a glycoprotein, the acid-labile subunit (ALS), to form a ternary complex with IGF-I or IGF-II. Each component of this trimer is growth hormone-dependent, and the hypoglycemic potential of circulating IGFs appears neutralized in this form. IGFs in the complex have a greatly extended circulating half-life, their stability being conferred by the presence of ALS, which is itself very stable in the circulation. IGFBP-1 does not appear to be a carrier of IGFs, but to act as an acute modulator of their metabolic activities. In this role it can be viewed as an insulin counter-regulator, blocking 'free' insulin-like activity during fasting or hypoglycemia. IGF-I administration causes complex changes in circulating IGFBPs, so that a detailed knowledge of their regulation is essential if the therapeutic potential of IGF-I is to be optimised.
胰岛素样生长因子（IGFs）的作用和生物利用度受一个由六种IGF结合蛋白组成的家族调控。IGFBP-3是主要的循环IGFBP，其独特之处在于它能与一种糖蛋白——酸不稳定亚基（ALS）结合，与IGF-I或IGF-II形成三元复合物。该三聚体的每个组分都依赖生长激素，循环IGFs的降血糖潜能在这种形式下似乎被中和。复合物中的IGFs循环半衰期大大延长，其稳定性由ALS赋予，而ALS本身在循环中非常稳定。IGFBP-1似乎不是IGFs的载体，而是其代谢活性的急性调节剂。在这一角色中，它可被视为胰岛素的反调节因子，在禁食或低血糖期间阻断“游离”胰岛素样活性。给予IGF-I会导致循环IGFBPs发生复杂变化，因此，如果要优化IGF-I的治疗潜力，详细了解其调控机制至关重要。
