Simian virus 40 rapidly lowers cAMP levels in mouse cells

The addition of SV40 to contact inhibited $\text{Balb}\text{3T3}$ cells causes a 2-fold decrease in intracellular cAMP levels. The levels reach a minimum 3 hours after virus addition, and after a few hours begin to rise toward normal. No significant changes in cAMP levels are observed after cells are exposed to UV-inactivated virus or are mock-infected. This is the earliest known effect of SV40 infection. We propose that SV40 induces host DNA synthesis by lowering cAMP levels.