Possible involvement of cyclic GMP in growth control of cultured mouse cells

Abstract

NON-TRANSFORMED fibroblastic cells in tissue culture exist in one of two reversible growth states, a state of rapid proliferation (growing) and a state of relative quiescence (resting)^1,2. Transition from a resting to a growing state can be accomplished by a variety of mitogenic agents including growth substances in animal sera, insulin and proteases. 3′, 5′-cyclic adenosine monophosphate (cyclic AMP) was implicated in this transition^3,4 in that the intracellular concentrations of cyclic AMP in resting cell cultures fall after brief exposure to mitogenic agents^3,4 and exogenous additions of high concentrations (10⁻⁴ to 10⁻³M) of dibutyryl cyclic AMP to the culture medium cause a partial reversal of the mitogenic response⁵. Kram and Tomkins⁶ have shown that exogenous additions of 3′, 5′-cyclic guanosine monophosphate (cyclic GMP) to the medium of cultured mouse cells can counteract the inhibitory effects of dibutyryl cyclic AMP upon some of the earliest events induced by a mitogenic signal (increased uptake of uridine, leucine, and 2-deoxy-glucose). We now report (1) that relatively high concentrations (10⁻⁶ to 10⁻⁴M) of cyclic GMP or its butyrated analogues when added to quiescent Balb/c 3T3 cultures can induce a substantial increase in DNA synthesis and (2) that within a few minutes of serum addition to quiescent cultures the intracellular concentration of cyclic GMP, as measured by two independent methods, rises by a factor of nine- to eleven-fold. Cyclic AMP and cyclic GMP concentrations were also measured throughout the remainder of the cell cycle.