because comparable extents of pdgf-induced tyrosine phosphorylation of the pdgf receptor were observed despite the differential pdgf-induced mitogenic response of sparse and confluent fibroblasts , we tentatively conclude that 1 ) pdgf-dependent tyrosine phosphorylation of the pdgf receptor is not tightly coupled to the propagation of the mitogenic signal and 2 ) density-dependent inhibition of growth does not reflect any measurable change in the quantity of kinase activity of the pdgf receptor .
C0032200
pdgf
C0018284
mitogenic