Philipps A F, Dvorák B, Anderson G G, Grille J G, Williams C S, Koldovský O
Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona College of Medicine, Tucson, Ariz., USA.
Biol Neonate. 2000;78(2):106-12. doi: 10.1159/000014258.
Bile from rats of different ages (suckling 10-12 days; weanling 30-33 days, and adult 60-70 days) was collected and studied for the presence of immuno- and receptor-assayable insulin-like growth factor-II (IGF-II) concentrations. Concentrations of RIA IGF-II in bile were highest in suckling rats (230 +/- 38 ng/ml) and lowest in adults (47 +/- 7 ng/ml). These concentrations were approximately twice those of the bile IGF-I concentration in sucklings, as measured in a previous study. Selected bile samples were also assayed using a competitive binding assay with a crude preparation of adult rat liver membranes bearing the IGF-II receptor. These studies confirmed the presence of receptor- (as well as immuno-) active IGF-II in bile. Since bile flow rates increased dramatically after the suckling period, bile delivery rates of IGF-II were normalized as picograms per gram body weight per hour. When such calculations were done, bile IGF-II delivery rates to the small intestine were highest in sucklings and weanlings in comparison to adult rats. Thus non-enterically derived (milk- and bile-borne) IGF-II delivery to the suckling small intestine can be approximated at roughly 1 microg/day. Unlike IGF-I, intravenously injected IGF-II could not be detected in suckling bile, suggesting a predominantly hepatic origin. From this study we conclude that there exists a significant delivery of receptor-active IGF-II to the gastrointestinal tract of rats of all ages.
收集不同年龄（10 - 12日龄的乳鼠；30 - 33日龄的断奶鼠，以及60 - 70日龄的成年鼠）大鼠的胆汁，研究其中可通过免疫测定和受体测定的胰岛素样生长因子-II（IGF-II）浓度。胆汁中放射免疫分析（RIA）IGF-II的浓度在乳鼠中最高（230±38 ng/ml），在成年鼠中最低（47±7 ng/ml）。这些浓度约为先前研究中测得的乳鼠胆汁IGF-I浓度的两倍。还使用与携带IGF-II受体的成年大鼠肝膜粗制品的竞争性结合测定法对选定的胆汁样本进行了测定。这些研究证实了胆汁中存在具有受体活性（以及免疫活性）的IGF-II。由于哺乳期后胆汁流速显著增加，IGF-II的胆汁输送率按每克体重每小时皮克进行了标准化。当进行此类计算时，与成年大鼠相比，乳鼠和断奶鼠向小肠的胆汁IGF-II输送率最高。因此，非肠道来源（来自乳汁和胆汁）的IGF-II向乳鼠小肠的输送量约为每天1微克。与IGF-I不同，静脉注射的IGF-II在乳鼠胆汁中无法检测到，这表明其主要起源于肝脏。从这项研究我们得出结论，在所有年龄的大鼠胃肠道中都存在大量具有受体活性的IGF-II的输送。
