Prostaglandin E1 induced changes in cyclic AMP levels in WI-38 human fibroblasts. Two different effects of cell density.

WI-38 lung diploid fibroblasts respond to protaglandin E1 with increased levels of cyclic adenosine 3':5'-monophosphate. This increase is affected by cell density in two ways: (a) The initial rate of accumulation of intracellular cyclic AMP increases with increasing cell density. (b) However, the elevated levels of cyclic AMP are more stably maintained in lower-density cells, and this stability decreases with increasing cell density. Cyclic AMP phosphodiesterase activities, as well as the efflux of intracellular cyclic AMP into the medium are similar at all cell densities.