Some mitogens cause rapid increases in free calcium in fibroblasts

Quiescent 3T3 fibroblasts grown on microcarrier beads and loaded with the Ca2+ indicator quin2 had a cytosolic free Ca2+ concentration ( Ca2+i) of 154 +/- 11 nM (SE; n = 32). Stimulation with the mitogens vasopressin, epidermal growth factor (EGF) or prostaglandin F2 alpha (PGF2 alpha) caused a very rapid increase in Ca2+i to a maximum of 200-500 nM after 60-90 s. Ca2+i declined thereafter to a level above that in quiescent cells which was maintained for at least 15 min. In contrast no immediate effects on Ca2+i were detected after the addition of the mitogens insulin or 12-O-tetradecanoylphorbol 13-acetate (TPA). These studies indicate that early changes in Ca2+i may be involved in the action on fibroblasts of some, but not all, mitogens.