Coordinate control of 3T3 cell proliferation by platelet-derived growth factor and plasma components.

DNA synthesis and cell division were measured in Swiss mouse 3T3 cells cultured in different concentrations of cell-free plasma-derived serum and increasing amounts of a platelet-derived growth factor. In plasma-derived serum alone, the cells were quiescent and they were arrested in the Go/G1 phase of the cell cycle. Addition of a platelet-derived growth factor to quiescent cells maintained in plasma-derived serum stimulated both DNA synthesis and cell division. When plasma components were present at high concentration (5%, vol/vol), the amount of platelet factor added to the cultures determined the number of cell doublings. Plasma-derived molecules were required for the platelet factor to stimulate DNA synthesis and cell division in the maximal number of cells. In addition, plasma components had to be present for recently divided cells to respond to the platelet factor. When 3T3 cells were cultured in excess platelet factor and limiting amounts of plasma-derived serum (0.5%, vol/vol), the cells underwent one doubling and then ceased to proliferate. Addition of fresh plasma-derived serum to these cells induced a second round of cell division. Plasma components and the platelet-derived growth factor acted in a coordinate fashion to regulate the proliferation of Swiss 3T3 cells.