Probst I, Jungermann K
Eur J Biochem. 1983 Sep 1;135(1):151-6. doi: 10.1111/j.1432-1033.1983.tb07630.x.
Evidence for a direct metabolic effect of insulin in isolated liver preparations is scarce. The stimulation of glycolysis by insulin previously demonstrated in monolayer cultures of adult rat hepatocytes [(1982) Eur. J. Biochem. 126, 271-278] was further investigated. The degree of stimulation varied with the age of the culture and amounted to 250%, 200%, 500% and 200% of the control value using cells at the culture age of 2 h, 24 h, 48 h, and 72 h, respectively. Half-maximal dose of insulin was 0.1 nM. Maximal stimulation was reached within 5 min and lasted for at least 4 h. Dexamethasone acted both as a long-term and short-term modulator. Long-term pretreatment of the cells with dexamethasone proved necessary to permit insulin action. In addition to this permissive action, pretreatment with dexamethasone reduced the insulin-independent basal glycolytic rate. In short-term experiments dexamethasone decreased the basal glycolytic flux, however, it did not affect the absolute increase in glycolysis brought about by insulin. The half-maximal dose of dexamethasone was 10 nM. The stimulatory effects of insulin may in part be attributed to the activation of pyruvate kinase. Insulin produced a left-shift of the substrate saturation curve, decreasing the K0.5 value for phosphoenolpyruvate.
在分离的肝脏制剂中，胰岛素直接代谢作用的证据很少。此前在成年大鼠肝细胞单层培养物中证实的胰岛素对糖酵解的刺激作用[(1982)欧洲生物化学杂志126, 271 - 278]得到了进一步研究。刺激程度随培养时间而变化，分别使用培养2小时、24小时、48小时和72小时的细胞时，刺激程度分别为对照值的250%、200%、500%和200%。胰岛素的半最大剂量为0.1 nM。最大刺激在5分钟内达到，并持续至少4小时。地塞米松可作为长期和短期调节剂。事实证明，用地塞米松对细胞进行长期预处理是胰岛素发挥作用所必需的。除了这种允许作用外，用地塞米松预处理还降低了胰岛素非依赖性基础糖酵解速率。在短期实验中，地塞米松降低了基础糖酵解通量，然而，它并不影响胰岛素引起的糖酵解绝对增加量。地塞米松的半最大剂量为10 nM。胰岛素的刺激作用可能部分归因于丙酮酸激酶的激活。胰岛素使底物饱和曲线左移，降低了磷酸烯醇丙酮酸的K0.5值。
