Hepatic and splenic microsomal electron transport system function, microsomal heme oxygenase activity, and microsomal drug metabolism have been examined in male Wistar rats bearing Murphy-Sturm lymphosarcoma 2 to 15 days following i.m. tumor transplantation. Hepatic microsomal cytochrome P450 and NADPH-cytochrome c reducÃ-ase activity decreased significantly [cytochrome P-450 nadir was 0.49 ± ...

Administration of 9a-fluoroprednisolone to mice bearing the corticoid-sensitive strain of Lymphosarcoma PI 798 resulted in a prompt regression of tumor size. This regression was accompanied by a selective decrease in tumor RNA. Tumor DNA con centration remained at control levels. These changes were preceded by an increased tumor ribonuclease activity in homogenates of tumor after the in vivoadm...

RNase activity increases in P1798 lymphoid tumors main tained in BALB/c mi ce that are undergoing irevitro drug-induced regression. Corticosteroids, 5-fluorouracil, vincristine, vinblastine, methotrexate, and triethylenemelamine produce re gression of appropriate sublines of P1798 lymphosarcoma as well as an increase in RNase activity. Numerous other agents tested had no effect either on tumor ...