RESPONSE TO PLATELET-DERIVED GROWTH-FACTOR BY PHENOTYPICALLY DIFFERENT CULTURED HUMAN AORTIC SMOOTH-MUSCLE CELLS

We investigated the effects of PDGF on DNA synthesis and mitogen-activ ated protein (MAP) kinase activity, and demonstrated that the adult in timal SMC was concentration-dependently stimulated by all PDGF isoform s in terms of both [H-3]thymidine incorporation and MAP kinase activat ion, with PDGF-BB and -AB being more potent than PDGF-AA. The intimal SMCs and the neonatal SMCs showed a similar response with regard to MA P kinase activation. On the other hand, the intimal SMCs expressed man y more PDGF receptors than the adult medial SMCs, which expressed a gr eater amount of PDGF-A chain mRNA and showed a lesser response to PDGF s. These results suggest that the intimal SMCs have a relatively high potential to react to exogenous PDGFs, whereas the adult medial SMCs d epend on endogenous or autocrine secretion of PDGF-AA.