Cell Cycle activation and ouabain-sensitive ion movements of 3T3 and C3H-10T½ fibroblasts

The introduction of either PGF2 alpha-(10(-7) M) or TPA (10(-7) M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2 alpha at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-10T1/2 cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10(-7) M TPA, whereas PGF2 alpha stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T1/2 cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2 alpha cannot be confirmed.