Fluctuations in phosphoribosyl pyrophosphate levels in monolayer tumor cell lines. Effects of drugs.

The concentration of PRPP (phosphoribosyl pyrophosphate) measured in tumor cells grown in monolayer showed a large variation with the various harvesting methods examined, including trypsinization. This variation could be reduced by a 1-h incubation of trypsinized cells as a suspension in Dulbecco's medium. After this preincubation these cell suspensions were suitable for the study of modulation of PRPP. One microM methotrexate caused a 2-3-fold increase and 1 mM N- phosphonoacetyl -L-aspartate a slight increase, but inosine and deoxyinosine drastically reduced PRPP concentrations. 5-Fluorouracil had no effect. This study demonstrates that metabolic parameters such as PRPP concentrations can be studied conveniently in suspensions of cells which are commonly cultivated as monolayers.