to investigate how cell population density influences the intracellular concentration of cyclic amp we have measured adenylate cyclase and cyclic amp phosphodiesterase activities and cyclic amp levels at various stages of cell density in normal rat-kidney ( nrk ) cells , which exhibit contact-inhibition of growth , and in normal chick-embryo fibroblasts ( cef ) , which do not show contact inhibition of growth under our conditions .
C0007634
normal
C0016030
fibroblasts