Hardin C D, Roberts T M
Department of Physiology, University of Missouri, Columbia 65212, USA.
J Mol Cell Cardiol. 1997 Apr;29(4):1207-16. doi: 10.1006/jmcc.1996.0356.
The aim of this study was to determine whether the pathways of glycolysis and glycogenolysis can be independently modulated by the provision of acetate or pyruvate as exogenous substrates. Hog carotid artery segments were allowed to replete glycogen stores to over 6 micromol/g of new 13C-labeled glycogen by incubation at 37 degrees C with 5 mM [1-13C]glucose for 6-16 h and then were isometrically contracted for 3 h with 80 mM KCl in the presence of 5 mM [2-13C]glucose and either 2 mM sodium acetate or 5 mM sodium pyruvate. Measurements were made of total lactate production, glucose utilization, glycogen utilization, isometric force, [2-13C]lactate and [3-13C]lactate production. Compared to experiments with glucose as the sole exogenous substrate, provision of pyruvate significantly decreased glucose utilization (by 28%) but insignificantly decreased glycogen utilization. In contrast, provision of acetate resulted in a statistically insignificant decrease in glucose utilization (by 23%) and an increase in glycogen utilization (by 20%). The fraction of [3-13C]pyruvate derived from glycogen that was converted to [3-13C]lactate was significantly decreased in the presence of acetate despite the enhanced glycogen utilization. Despite these alterations in cellular energy balance, isometric force generation and maintenance was similar for all experimental groups. This differential regulation of glycolysis and glycogenolysis may either reflect the compartmentation of these pathways or suggest a novel regulation of carbohydrate metabolism in vivo.
本研究的目的是确定糖酵解和糖原分解途径是否可通过提供乙酸盐或丙酮酸盐作为外源性底物而被独立调节。将猪颈动脉段在37℃下与5 mM [1-¹³C]葡萄糖孵育6 - 16小时，使糖原储备补充至超过6 μmol/g的新的¹³C标记糖原，然后在5 mM [2-¹³C]葡萄糖以及2 mM乙酸钠或5 mM丙酮酸钠存在的情况下，用80 mM氯化钾进行3小时的等长收缩。测量总乳酸生成量、葡萄糖利用率、糖原利用率、等长力、[2-¹³C]乳酸和[3-¹³C]乳酸生成量。与以葡萄糖作为唯一外源性底物的实验相比，提供丙酮酸盐显著降低了葡萄糖利用率（降低28%），但对糖原利用率的降低不显著。相反，提供乙酸盐导致葡萄糖利用率有统计学意义的轻微降低（降低23%），而糖原利用率增加（增加20%）。尽管糖原利用率提高，但在乙酸盐存在的情况下，源自糖原并转化为[3-¹³C]乳酸的[3-¹³C]丙酮酸盐的比例显著降低。尽管细胞能量平衡发生了这些变化，但所有实验组的等长力产生和维持情况相似。糖酵解和糖原分解的这种差异调节可能反映了这些途径的区室化，或者提示了体内碳水化合物代谢的一种新调节方式。
