Endogenous Glucose Production during Constant Glucose Infusion in the Newborn Lamb
Endogenous Glucose Production during Constant Glucose Infusion in the Newborn Lamb
复制标题
新生羔羊恒定葡萄糖输注过程中内源性葡萄糖的产生
作者：
R. Cowett;J. Susa;W. Oh;R. Schwartz
总结：内源性肝葡萄糖生成的迅速减少是对外源性葡萄糖输注的成熟（成人）反应的特征。我们已经在26只未麻醉的混种足月羔羊的新生期测试了这一假设的有效性，并在8只4 - 5个月大的混种绵羊中进行了比较。禁食7小时后，测定基础血浆葡萄糖、胰岛素和胰高血糖素浓度，随后足月羔羊在6小时内不接受葡萄糖或接受5.7、11.7或21.7 mg葡萄糖/kg/min，5个月大的绵羊不接受葡萄糖或接受5.7 mg葡萄糖/kg/min。Steele的恒定输注技术，在50分钟的周转期内使用3 H6放射性标记的葡萄糖，随后6小时输注0.45%新生动物和成年动物在禁食14小时后均保持恒定的血浆葡萄糖浓度和葡萄糖比活性在周转期间。内源性葡萄糖的产生持续存在于足月羔羊中，直到外源性葡萄糖输注达到21.7 mg/kg/min的速率。相反，成年羔羊以5.7 mg/kg/min的外源性葡萄糖输注速率降低其内源性葡萄糖的产生。在内源性葡萄糖产生速率显著降低时，新生羔羊的血浆胰岛素水平是成年绵羊的5倍。在血浆葡萄糖浓度和葡萄糖比活性的稳态条件下，我们的数据表明，与4-5月龄的老绵羊相比，新生羔羊的内源性葡萄糖产生的控制不精确。缺乏精确控制可能是由于肝脏对胰岛素的敏感性降低。
Summary: Prompt diminution of endogenous hepatic glucose production is characteristic of the mature (adult) response to exogenous glucose infusion. We have tested the validity of this hypothesis in the neonatal period in 26 unanesthetized mixed breed term lambs and for comparison in eight 4− to 5-month-old mixed breed sheep. After a 7-hr fast, basal plasma glucose, insulin, and glucagon concentrations were determined following which the term lambs received either no glucose or 5.7, 11.7, or 21.7 mg glucose/kg/min over a period of 6 hr, and the 5-month-old sheep received either none or 5.7 mg glucose/kg/min. Glucose turnover was determined by the prime-constant infusion technique of Steele using 3H6 radiolabeled glucose during a 50-min turnover period which followed the 6-hr infusion of 0.45% saline or varying doses of glucose following the onset of fasting by 14 hr. Both newborn and adult animals maintained a constant plasma glucose concentration and glucose specific activity during the turnover period. Endogenous glucose production persisted in the term lamb until the exogenous glucose infusion reached the rate of 21.7 mg/kg/min. In contrast, the adult lambs reduced their endogenous glucose production with an exogenous glucose infusion rate of 5.7 mg/kg/min. At the time the endogenous glucose production rates were significantly reduced, the plasma insulin level in the newborn lamb was 5-fold greater than that of the adult sheep.Under steady state conditions of plasma glucose concentration and glucose specific activity, our data suggest that there is imprecise control of endogenous glucose production in the newborn lamb in contrast to the older sheep of 4–5 months of age. The absence of precise control may be due to decreased hepatic sensitivity for insulin.