Parrilla R, Ayuso-Parrilla M S
Pflugers Arch. 1976 Mar 11;362(1):49-54. doi: 10.1007/BF00588680.
Glucose production was measured in isolated rat livers perfused with 100 ml of blood-free recirculating medium. The gluconeogenic rate using L-alanine as substrate was only 55% of that obtained with L-lactate. The steady-state concentration of gluconeogenic and tricarboxylic acid cycle intermediates were measured in freeze clamped biopsies. Livers perfused with L-lactate displayed higher concentrations of malate, alpha-glycerophosphate and beta-hydroxybutyrate probably as a result of a higher state of reduction of the nicotinamide system. Hexose-phosphate intermediates were also increased when L-lactate was the substrate. Phosphoenolpyruvate and 3-phosphoglycerate were considerably elevated when L-alanine was the glucose precursor. Livers perfused with L-lactate displayed higher cytosolic concentration of all the tricarboxylic acid cycle intermediates except oxaloacetate while glutamate was slightly and aspartate considerably higher when alanine was the substrate. In the mitochondrial compartment the pattern of distribution tended to be the opposite; that is, livers perfused with L-lactate showed lower concentrations of all the intermediates except alpha-ketoglutarate. The mitochondrial: cytosolic metabolite gradients of all the intermediates whose distribution was studied were higher in livers perfused with L-alanine. The relevance of these findings to the observed differences in the gluconeogenic fluxes are discussed.
在灌注100毫升无血循环培养基的离体大鼠肝脏中测量葡萄糖生成。以L-丙氨酸为底物的糖异生速率仅为以L-乳酸为底物时的55%。在冷冻钳夹活检组织中测量糖异生和三羧酸循环中间产物的稳态浓度。用L-乳酸灌注的肝脏中，苹果酸、α-甘油磷酸和β-羟基丁酸的浓度较高，这可能是由于烟酰胺系统的还原状态较高。当L-乳酸为底物时，磷酸己糖中间产物也会增加。当L-丙氨酸作为葡萄糖前体时，磷酸烯醇丙酮酸和3-磷酸甘油酸显著升高。用L-乳酸灌注的肝脏中，除草酰乙酸外，所有三羧酸循环中间产物的胞质浓度均较高，而当丙氨酸为底物时，谷氨酸略有升高，天冬氨酸则显著升高。在线粒体区室中，分布模式往往相反；也就是说，用L-乳酸灌注的肝脏中，除α-酮戊二酸外，所有中间产物的浓度均较低。在以L-丙氨酸灌注的肝脏中，所有研究其分布的中间产物的线粒体：胞质代谢物梯度更高。讨论了这些发现与观察到的糖异生通量差异的相关性。
