Larrabee M G
J Neurochem. 1980 Jul;35(1):210-31. doi: 10.1111/j.1471-4159.1980.tb12508.x.
Dorsal root ganglia from the lumbar region of chicken embryos 14--16 days old were incubated at 37 degrees in modified McCoy's culture medium containing [1-(14)C]glucose or [6-(14)C]glucose and sometimes 32Pi. A volume of 10 microliters of medium was used for four ganglia (dry weight approx. 90 micrograms). The output of 14CO2 was measured continuously. Incorporation of 14C into tissue constituents and into products released to the medium was measured after incubation for 3--17 h. Among nine radioactive components resolved in paper chromatograms of ganglion constituents, the most 14C was found in lipids and on materials remaining at the origin. Only the lipids and the origin materials were detectably labeled by 32Pi. Only relatively small amounts of 14C from [6-(14)]glucose were found in chromatographic regions that should contain intermediates of the pentose cycle. At least five labeled products were released to the bathing medium. Among these, the largest amount of 14C was found in lactic acid. A second component released, possibly alanine, also received considerable 14C. No 32P was detected in products in the medium. The rate of glucose uptake remained relatively constant as the concentration of glucose in the medium declined nearly 10-fold during prolonged experiments. Two new dynamic models of glucose metabolism successfully explained the time courses and magnitudes of previously reported 14CO2 outputs from [1-(14)C]glucose, [2-(14)C]-glucose, and [6-(14)C]glucose. These models are based on the assumption that glucose carbon was delayed on its way to CO2 in a pool of intermediates early in the metabolic chain and in a second pool either in or before the citric acid cycle. Both models assigned the pentose cycle to one cellular compartment, and incorporation into slowly-turning-over substances to another cellular compartment. According to both models, not more than one-half of the glyceraldehyde-P produced by the pentose cycle was converted to fructose-6-P, while at least half of this and other fructose-6-P from the pentose cycle was recycled into it. These conclusions differ from those from a previous model, which assumed that glucose carbon was delayed in a pool related to the pentose cycle; that model had suggested full recycling of both the glyceraldehyde-P and the fructose-6-P produced by the pentose cycle. In the citric acid cycle the efficiency of recycling was over 80%, according to all models. All models demonstrated the large differences that can occur in the metabolic handling of carbons 1, 2, and 6 of glucose. These differences need consideration in any description of the partitioning of glucose metabolism between alternative pathways.
将14至16日龄鸡胚腰椎区域的背根神经节置于37摄氏度的改良 McCoy 培养基中培养，培养基中含有[1-(14)C]葡萄糖或[6-(14)C]葡萄糖，有时还含有32Pi。10微升培养基用于培养四个神经节（干重约90微克）。连续测量14CO2的释放量。培养3至17小时后，测量14C掺入组织成分和释放到培养基中的产物中的量。在神经节成分的纸色谱图中分辨出的九种放射性成分中，脂质和原点处剩余的物质中14C含量最高。只有脂质和原点处的物质能被32Pi检测到标记。在应该包含戊糖循环中间体的色谱区域中，仅发现相对少量的来自[6-(14)]葡萄糖的14C。至少有五种标记产物释放到了培养液中。其中，乳酸中14C含量最高。释放出的第二种成分可能是丙氨酸，也含有相当数量的14C。在培养基中的产物中未检测到32P。在长时间实验中，随着培养基中葡萄糖浓度下降近10倍，葡萄糖摄取速率保持相对恒定。两种新的葡萄糖代谢动态模型成功解释了先前报道的[1-(14)C]葡萄糖、[2-(14)C]葡萄糖和[6-(14)C]葡萄糖产生的14CO2释放量的时间进程和大小。这些模型基于这样的假设：葡萄糖碳在代谢链早期的中间体池中以及在柠檬酸循环中或之前的第二个池中，在其转化为CO2的过程中会有延迟。两种模型都将戊糖循环分配到一个细胞区室，而将掺入缓慢周转物质的过程分配到另一个细胞区室。根据这两种模型，戊糖循环产生的甘油醛-P中不超过一半转化为果糖-6-P，而戊糖循环产生的这种果糖-6-P以及其他果糖-6-P中至少有一半会再循环回戊糖循环。这些结论与先前的模型不同，先前的模型假设葡萄糖碳在与戊糖循环相关的池中延迟；该模型曾提出戊糖循环产生的甘油醛-P和果糖-6-P都完全再循环。在柠檬酸循环中，根据所有模型，再循环效率超过80%。所有模型都表明，葡萄糖的1、2和6号碳在代谢处理上可能存在很大差异。在描述葡萄糖代谢在替代途径之间的分配时，需要考虑这些差异。
