Some mitogens cause rapid increases in free calcium in fibroblasts

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Abstract
Quiescent 3T3 fibroblasts grown on microcarrier beads and loaded with the [Ca 2+ ] indicator quin2 had a cytosolic free Ca 2+ concentration ([Ca 2+ ] i ) of 154 ± 11 nM (SE; n = 32). Stimulation with the mitogens vasopressin, epidermal growth factor (EGF) or prostaglandin F 2α (PGF 2α ) caused a very rapid increase in [Ca 2+ ] i to a maximum of 200–500 nM after 60–90 s. [Ca 2+ ] 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 [Ca 2+ ] i were detected after the addition of the mitogens insulin or 12- O -tetradecanoylphorbol 13-acetate (TPA). These studies indicate that early changes in [Ca 2+ ] i may be involved in the action on fibroblasts of some, but not all, mitogens.