Vissing J, Sonne B, Galbo H
Department of Medical Physiology B, Panum Institute, University of Copenhagen, Denmark.
J Appl Physiol (1985). 1988 Dec;65(6):2552-7. doi: 10.1152/jappl.1988.65.6.2552.
The importance of metabolic feedback regulation vs. feedforward regulation of hepatic glucose production (HGP) during exercise was investigated in rats by infusing glucose intravenously from the onset of running. Glucose infusion equaled the average exercise-induced increase from basal to steady state in HGP found in saline-infused control rats. Rats were studied at two work loads, running at 21 (series I) or 18 m/min (series II) for 35 min. Glucose turnover was measured by means of an intravenous [3H]glucose infusion. HGP was suppressed by glucose infusion corresponding to the infused amount of glucose in both series, except for late in exercise in series I, where HGP plus infused glucose tended to exceed HGP in saline-infused rats (P less than 0.10). Muscle glycogenolysis and fat metabolism were similar in both groups in the two series. Plasma glucose was never elevated, whereas insulin was, in glucose- vs. saline-infused rats of both series. Plasma catecholamines were lower in glucose- compared with saline-infused rats in series II. In conclusion, HGP is very sensitive to metabolic feedback inhibition at low exercise intensities. Feedforward control of HGP may play a role at higher work loads (series I). Exogenously supplied glucose, in moderate amounts, may replace HGP specifically without concomitant changes in mobilization of other substrates.
通过在大鼠跑步开始时静脉输注葡萄糖，研究了运动期间肝脏葡萄糖生成（HGP）的代谢反馈调节与前馈调节的重要性。葡萄糖输注量等同于在输注生理盐水的对照大鼠中发现的从基础状态到稳态的运动诱导的HGP平均增加量。在两种工作负荷下对大鼠进行研究，以21米/分钟（系列I）或18米/分钟（系列II）的速度跑步35分钟。通过静脉输注[3H]葡萄糖来测量葡萄糖周转率。在两个系列中，葡萄糖输注均抑制了HGP，抑制程度与输注的葡萄糖量相对应，但系列I运动后期除外，此时HGP加上输注的葡萄糖往往超过输注生理盐水大鼠的HGP（P<0.10）。在两个系列的两组中，肌肉糖原分解和脂肪代谢相似。在两个系列中，葡萄糖输注大鼠与输注生理盐水大鼠相比，血浆葡萄糖从未升高，而胰岛素升高。在系列II中，与输注生理盐水的大鼠相比，葡萄糖输注大鼠的血浆儿茶酚胺水平较低。总之，在低运动强度下，HGP对代谢反馈抑制非常敏感。HGP的前馈控制可能在较高工作负荷（系列I）下起作用。适量的外源性葡萄糖可以特异性地替代HGP，而不会伴随其他底物动员的变化。
