Pyruvate kinase and the interaction of amino acid and carbohydrate metabolism in solid tumors

The interaction between glycolysis, glutaminolysis and tumor growth in WAG/ Fra mu/mu rats has been investigated. Small tumors are characterized by a l ow conversion of glucose to lactate whereas the conversion of glutamine to lactate is high. In medium sized tumors the flow of glucose to lactate as w ell as oxygen utilization are increased whereas glutamine and serine consum ption are reduced. At this stage the tumor cells start with glutamate and a lanine production. Large tumors are characterized by a low oxygen and gluco se supply but a high glucose and oxygen utilization rate. The conversion of glucose to glycine, alanine, glutamate, glutamine, and proline reaches hig h values and the amino acids are released. Pyruvate kinase increases with t umor weight and is positively correlated with an increase in glucose and ox ygen utilization. The shift from glutamate consumption to glutamate product ion is correlated with an increase in glutamate dehydrogenase and glutamate oxaloacetate transaminase activity.