Base-exchange and cell growth in 3T6 mouse fibroblasts

Synthesis of phosphatidyl serine by base-exchange and DNA synthesis both declined rapidly in mouse fibroblast cultures upon withdrawal of serum from nutrient medium. Base-exchange returned to control levels within 3 h after the addition of serum, while DNA synthesis lagged by 10 h. Phosphatidyl serine synthesis is thus an early response of 3T6 cells to mitogenic signals.