Cline G W, Shulman G I
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
J Biol Chem. 1991 Mar 5;266(7):4094-8.
In order to examine the pathways of hepatic glycogen repletion in the periportal and perivenous zones of the liver, [1-13C]glucose (99% enriched) was infused intraduodenally into conscious, 24-h fasted rats for 3 h. The liver was then quickly perfused in situ, and the cytoplasmic contents of the periportal and perivenous hepatocytes were selectively sampled by modification of the dual-digitonin-pulse technique (Quistorff, B., and Grunnet, N. (1987) Biochem. J. 243, 87-95). The 13C isotopic enrichment at each carbon position of the glucosyl units of hepatic glycogen was determined by 13C NMR and that of the C-1 position by gas chromatography-mass spectroscopy. From comparison of hepatic glycogen repleted by direct incorporation of plasma glucose (glucose----glucose-6-P----glucose-1-P----UDP-glucose----glycogen) was calculated to be 29% in the periportal zone and 35% in the perivenous zone, assuming equal glycogen synthetic rates within the two zones. Thus, the majority of glycogen is derived by an indirect route (glucose--------3-carbon unit--------glucose --------UDP-glucose--------glycogen) in both the periportal zone and in the perivenous zone. In conclusion, in a 24-h fasted rat there does not appear to be a major difference between the periportal and perivenous hepatocytes in the percent of glycogen synthesized by the direct pathway following a glucose load.
为了研究肝脏门静脉周围和肝静脉周围区域肝糖原补充的途径，将[1-¹³C]葡萄糖（富集度99%）经十二指肠内注入清醒的、禁食24小时的大鼠体内3小时。然后迅速在原位灌注肝脏，通过改良的双洋地黄皂苷脉冲技术（Quistorff, B., and Grunnet, N. (1987) Biochem. J. 243, 87 - 95）选择性采集门静脉周围和肝静脉周围肝细胞的细胞质内容物。通过¹³C NMR测定肝糖原葡萄糖基单位每个碳位置的¹³C同位素富集度，通过气相色谱 - 质谱法测定C - 1位置的富集度。通过比较由血浆葡萄糖直接掺入补充的肝糖原（葡萄糖→葡萄糖 - 6 - 磷酸→葡萄糖 - 1 - 磷酸→UDP - 葡萄糖→糖原），假设两个区域内糖原合成速率相等，计算得出在门静脉周围区域为29%，在肝静脉周围区域为35%。因此，在门静脉周围区域和肝静脉周围区域，大多数糖原是通过间接途径（葡萄糖→三碳单位→葡萄糖→UDP - 葡萄糖→糖原）产生的。总之，在禁食24小时的大鼠中，葡萄糖负荷后通过直接途径合成糖原的百分比，门静脉周围和肝静脉周围肝细胞之间似乎没有显著差异。
