Variation in potassium transport properties of mouse 3T3 cells as a result of subcultivation

Unidirectional potassium influx and the fraction of this influx sensitive to ouabain, an inhibitor of the (Na + K) activated ATPase, have been evaluated as a function of subcultivation of the 3T3 and SV40 transformed 3T3 cell. Total and ouabain‐sensitive K influx change little over approximately 50 passages of the transformed 3T3 cell. In contrast, these components of K influx increase nearly 5‐fold over a similar number of passages of the 3T3 cell. During early passages total and ouabain‐sensitive K influx of the 3T3 cell are below that of the SV40 3T3 cell on a per cell volume basis. At later passages the magnitude of these components of K transport exceed those found in the SV40 3T3 cell. Previous studies have reported the ouabain‐sensitive uptake of K and the levels of (Na + K) activated ATPase as being higher, lower or equivalent in the 3T3 versus transformed 3T3 cell. The present data suggest these differences may result from the degree to which the cells were passaged at the time of the experiments. Evaluation of previous studies substantiates this conclusion.