Decreased content of reduced and oxidized nicotinamide-adenine dinucleotide phosphate in rat hepatomas

Tissue contents of NADPH and NADP+ were measured in freeze-clamped samples of normal rat liver and in four transplantable rat hepatomas covering a wide range of growth rates. Lowry cycling procedures were employed for analysis, using alkaline extracts for NADPH and acid extracts for NADP+. The mean NADPH content in 33 normal livers was 515 nmol/g wet weight, and mean NADP+ content was 311 nmol/g wet weight. In the four hepatomas, the amounts of both NADPH and NADP+ were low, and the extent of decrease correlated with tumor growth rate. In the slowly growing hepatoma 9618A, total NADP was slightly decreased (63% control) and more extensive decreases were observed in the medium growth rate tumors 47C and 8999 (38% and 19%, respectively, of control). In the rapidly growing hepatoma 3924A, total NADP was drastically decreased to 3% of the control liver value. Measurement of NADPH and NADP+ recovery from extracts of hepatoma 3924A showed that there were no inhibitors that might have blocked the activity of the assay enzymes. The NADPH/NADP+ ratio was close to the normal liver value in all four hepatomas. A 30-sec period of ischemia did not cause significant change in NADPH, but gave 33% decrease in liver NADP+. A 5-min period of ischemia decreased NADP+ to 50% of the zero-time value in liver, and to 71% in hepatoma 3924A, but was without effect on NADPH.