Sistare F D, Haynes R C
J Biol Chem. 1985 Oct 15;260(23):12761-8.
Hepatocytes, isolated from fasted rats, were incubated with graded concentrations of lactate and pyruvate, at a mean constant ratio of 10-13:1, to alter systematically the concentrations of gluconeogenic intermediate metabolites and rates of glucose production. By analyzing glucose production rates as a function of corresponding concentrations of extracellular pyruvate, cytosolic oxalacetate, and cellular 3-phosphoglycerate in the presence and absence of hormones and assuming no primary activation of phosphoenolpyruvate carboxykinase, estimates were made of the relative contributions of stimulation of formation of cytosolic oxalacetate and inhibition of pyruvate kinase to hormonal stimulations of gluconeogenesis. Addition of dexamethasone, glucagon, or angiotensin II did not cause a shift in the relationship between cellular 3-phosphoglycerate concentrations and rates of glucose production, indicating that there was no effect of these agents on the reactions involved in conversion of phosphoenolpyruvate to glucose. All three agents shifted the relationships between rates of glucose production and both cytosolic oxalacetate and extracellular pyruvate. The following conclusions were drawn from computer analyses of these results. At low concentrations of pyruvate, stimulation of oxalacetate production and pyruvate kinase inhibition were approximately equally contributory to the overall stimulations of gluconeogenesis by angiotensin II and dexamethasone. At higher pyruvate concentrations, pyruvate kinase inhibition by angiotensin II played a greater role, accounting for 90% of the overall stimulation. For dexamethasone, as the pyruvate concentration was increased, stimulation of gluconeogenesis resulting from enhanced formation of oxalacetate diminished as did overall stimulation of gluconeogenesis. Glucagon addition resulted in an inhibition of pyruvate kinase flux that accounted for 75% of the hormone's overall effect at low pyruvate concentrations; this increased to 95% at high pyruvate concentrations.
从禁食大鼠中分离出肝细胞，将其与梯度浓度的乳酸和丙酮酸一起孵育，乳酸与丙酮酸的平均恒定比例为10 - 13:1，以系统地改变糖异生中间代谢物的浓度和葡萄糖生成速率。通过分析在有无激素存在的情况下，葡萄糖生成速率作为细胞外丙酮酸、胞质草酰乙酸和细胞内3 - 磷酸甘油酸相应浓度的函数，并假设磷酸烯醇式丙酮酸羧激酶无初级激活，估算了胞质草酰乙酸形成的刺激作用和丙酮酸激酶抑制作用对激素刺激糖异生的相对贡献。添加地塞米松、胰高血糖素或血管紧张素II并未导致细胞内3 - 磷酸甘油酸浓度与葡萄糖生成速率之间的关系发生偏移，这表明这些试剂对磷酸烯醇式丙酮酸转化为葡萄糖所涉及的反应没有影响。所有这三种试剂都改变了葡萄糖生成速率与胞质草酰乙酸和细胞外丙酮酸之间的关系。从这些结果的计算机分析中得出了以下结论。在低丙酮酸浓度下，草酰乙酸生成的刺激作用和丙酮酸激酶的抑制作用对血管紧张素II和地塞米松对糖异生的总体刺激作用的贡献大致相等。在较高的丙酮酸浓度下，血管紧张素II对丙酮酸激酶的抑制作用发挥了更大的作用，占总体刺激作用的90%。对于地塞米松，随着丙酮酸浓度的增加，草酰乙酸生成增强导致的糖异生刺激作用减弱，糖异生的总体刺激作用也减弱。添加胰高血糖素导致丙酮酸激酶通量受到抑制，在低丙酮酸浓度下，这占该激素总体作用的75%；在高丙酮酸浓度下，这一比例增加到95%。
