Compartmentation of hexokinase in rat heart. A critical factor for tracer kinetic analysis of myocardial glucose metabolism.
Compartmentation of hexokinase in rat heart. A critical factor for tracer kinetic analysis of myocardial glucose metabolism.
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大鼠心脏中己糖激酶的区室。
DOI：
10.1172/jci116076
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Taegtmeyer,H
中科院分区：
文献类型：
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作者：
Russell3rd,RR;Mrus,JM;Mommessin,JI;Taegtmeyer,H
2-脱氧葡萄糖的放射性标记类似物被广泛用于追踪细胞培养物、整个器官和完整动物中的葡萄糖代谢，尽管这些化合物和葡萄糖之间存在转运和磷酸化的动力学差异。本研究旨在确定胰岛素刺激对2-脱氧葡萄糖磷酸化的影响，与葡萄糖相比，在完整的生理盐水灌注的工作大鼠心脏。当比较生理水平胰岛素（13 microU/ml）存在或不存在的情况下的葡萄糖利用率时，氚化葡萄糖测定的葡萄糖利用率与[14 C]2-脱氧葡萄糖累积估计的葡萄糖利用率不同。在胰岛素存在下灌注的心脏中，由[14 C]2-脱氧葡萄糖6-磷酸占的单磷酸化己糖的分数显著降低。此外，在胰岛素刺激的心脏中，与组织提取物的线粒体部分相关的己糖激酶活性增加。虽然这种重新分配的己糖激酶的线粒体不影响葡萄糖的表观亲和力常数，结合到线粒体的己糖激酶表现出8.5倍的减少，在2-脱氧葡萄糖的亲和力相比，存在于胞质组分中的己糖激酶。这些发现与胰岛素介导的葡萄糖优先摄取和磷酸化相一致。结果还暗示己糖激酶的再分布和胰岛素对其对示踪剂和示踪剂的亲和力的差异效应是“集总常数”（即，用于将2-脱氧葡萄糖等同于葡萄糖摄取的校正因子）。当用2-脱氧葡萄糖法评估局部心肌葡萄糖代谢时，必须考虑到这些变化。
Radiolabeled analogues of 2-deoxyglucose are widely used to trace glucose metabolism in cell cultures, whole organs, and intact animals, although kinetic differences in transport and phosphorylation between these compounds and glucose exist. The present studies were undertaken to determine the effects of insulin stimulation on the phosphorylation of 2-deoxyglucose compared to glucose in the intact, saline-perfused working rat heart. Rates of glucose utilization determined from tritiated glucose differed from rates estimated from the accumulation of [14C]2-deoxyglucose in a nonconstant manner when comparing rates in the absence or presence of physiologic levels of insulin (13 microU/ml). The fraction of monophosphorylated hexoses that was accounted for by [14C]2-deoxyglucose 6-phosphate was dramatically decreased in hearts perfused in the presence of insulin. Additionally, hexokinase activity associated with the mitochondrial fraction of tissue extracts was increased in hearts stimulated by insulin. While this redistribution of hexokinase to the mitochondria did not affect the apparent affinity constant for glucose, hexokinase bound to mitochondria exhibited an 8.5-fold decrease in the affinity for 2-deoxyglucose when compared with hexokinase present in the cytosolic fraction. The findings are consistent with an insulin-mediated preferential uptake and phosphorylation of glucose compared to deoxyglucose. The results also imply that the redistribution of hexokinase and the differential effect of insulin on its affinity for tracer and tracee are responsible for changes in the "lumped constant" (i.e., the correction factor used to equate 2-deoxyglucose to glucose uptake). These changes must be taken into account when regional myocardial glucose metabolism is assessed by the 2-deoxyglucose method.