METABOLISM OF 6-MERCAPTOPURINE RIBONUCLEOSIDE BY EHRLICH ASCITES CARCINOMA CELLS

Abstract

Ribonucleoside derivatives of 6-mercaptopurine (6-MP) and other purine bases were rapidly catabolized when incubated with Ehrlich ascites carcinoma cells in vitro. The catabolism of purine ribonucleosides proceeded by way of phosphorolytic cleavage of the glycosidic linkage and resulted in accumulation of the liberated base in the incubation medium. The ribosyl portions of ribonucleoside substrates were utilized with the formation of lactate, which also appeared extracellularly.Cells of a 6-MP-resistant subline of the Ehrlich ascites tumor degraded 6-MP ribonucleoside (6-MPR) at rates comparable to those of the parent line. This finding, when considered with other characteristics of the resistant line of cells, implied that cleavage of 6-MPR took place in a cell compartment from which inosinate pyrophosphorylase was absent.