Interaction of vasoactive intestinal peptide with HeLa cells: activation of cyclic AMP-dependent protein kinase and lack of effect on DNA synthesis

Vasoactive intestinal peptide (VIP) stimulated protein kinase activity in HeLa cells. Maximal activation by the peptide required the simultaneous presence of a phosphodiesterase inhibitor. The response was dose-dependent in the 0.3–10 nM range, half-maximal stimulation being observed at 1 nM VIP. This value agrees with the concentration of VIP required for half-maximal stimulation of cyclic AMP production as well as with the K_d of the high affinity binding sites for VIP in the same cell system (15). Secretin also stimulated protein kinase activity but with a 300-times lower potency than VIP. When DNA synthesis in Hela cells was studied, no effect of VIP could be seen in a 0.1–100 nM range of peptide concentration.