The Hexose Monophosphate Pathway in Ethylnitrosourea Induced Tumors of the Nervous System

Respiration studies in vitro, in which tissue slices were incubated with [1‐14C]glucose or [6‐14C]glucose and 14CO2 collected, resulted in C‐1/C‐6 14CO2 ratios that were higher in slices of tumor and newborn brain than in slices of adult brain. In adult brain, the C‐1/C‐6 14CO2 ratio averaged close to unity. In slices of tumor and newborn brain however, the mean C‐1/C‐6 ratio was greater than three. Addition of phenazine methosulfate (PMS) increased conversion of [1‐14C]glucose to 14CO2 in slices of normal adult brain 5‐fold, and in slices of newborn brain and tumor, approx 12‐fold. Injection of animals with 6‐aminonicotinamide (6‐AN) decreased conversion of [1‐14C]glucose in slices of normal brain 30% but decreased conversion in tumor slices by 80%. Evidence supports the presence of an active hexose monophosphate pathway (HMP) in tumors of the nervous system regulated in part by available NADP+ levels. Inhibition by 6‐AN was more effective in tumors than in normal adult brain.