Effect of chemotherapy on the energy and protein metabolism of children near the end of treatment for acute lymphoblastic leukemia.

Eight children in the final 3 mo of chemotherapy for acute lymphoblastic leukemia were studied while on oral 6-mercaptopurine (6MP) maintenance therapy and then again 4-9 mo after chemotherapy had been completed. Six of the eight were also studied a second time while on 6MP in the 24-h period after receiving intravenous methotrexate (MTX). 6MP reduced protein oxidation after a test meal and reduced fasting urinary urea excretion by enhancing the reutilization of endogenous amino acids for protein synthesis. MTX had no detectable effects on protein metabolism but reduced overnight carbohydrate utilization by enhancing fat utilization. A similar enhancement of fat utilization was evident after a test meal. The two drugs in combination resulted in effects on protein and energy metabolism that were the sum of the individual effects plus an increase in the rate of whole-body protein turnover and synthesis.