Intracellular lactic dehydrogenase and phosphohexose isomerase activity in leukaemia and malignant lymphoma

Intracellular activities of total lactic dehydrogenase (LDH) and phosphohexose isomerase (PHI) were investigated in the leukaemic cells of 14 patients with acute myeloid leukaemia (AML), five with chronic myeloid leukaemia (CML), seven with acute lymphoblastic leukaemia (ALL), 19 with chronic lymphocytic leukaemia (CLL), 16 with leukaemic non-Hodgkin's lymphoma (NHL) and in the lymphocytes of 14 normal persons. Intracellular total LDH-activity of the blasts of AML and ALL was in the same range as the normal lymphocytes. Patients with CLL and NHL had significantly lower levels (P less than 0.01) of total intracellular LDH than the controls. Intracellular PHI activity was consistently lower in the lymphoid malignancies (ALL, CLL, NHL) than in normal lymphocytes (P less than 0.05), or in leukaemic myeloblasts (P less than 0.01). The intracellular LDH/PHI index of the leukaemic lymphoblasts was significantly elevated as compared to lymphocytes from normal subjects (P less than 0.0001) or to leukaemic cells from patients with AML (P less than 0.001), with CLL (P less than 0.0001) or with NHL (P less than 0.001). The patients with CLL and NHL, on the other hand, had significantly lower levels of LDH/PHI ratio than the normal subjects (P less than 0.0001 and P less than 0.025 respectively).