Adenosine 3',5'-cyclic monophosphate and contact inhibition.

Abstract

Summary Adenosine 3′,5′-cyclic monophosphate (cAMP) and cyclic nucleotide phosphodiesterase were assayed in strain L cells from the 2nd to the 6th day of incubation. cAMP increases markedly when the culture reaches confluency on the 4th day of incubation. The phosphodiesterase increased in a similar but less dramatic manner. cAMP and cyclic nucleotide phosphodiesterase were measured in two nontumorigenic cell lines and five tumorigenic cell lines at confluency. The level of cAMP is higher in the nontumorigenic cultures and is related to the population-doubling time of the cells. It is proposed that contact inhibition of growth may be mediated by activation of adenyl cyclase in the cell membranes with subsequent rise in cellular cAMP.