AbstractWe used a baculovirus vector/insect host cell system to express cDNA clones of PDGF A genes from mouse and frog (Xenopus laevis). The insect host cells process PDGF A subunits from either frogs or mice into biologically active AA homodimers with yields in the range of 0.5-1.0 mg/liter of culture medium. The recombinant PDGFs can be metabolically labeled with35S-cysteine for use in radioreceptor and radioimmunoassays. Neutralizing polyclonal antisera can be raised against the mouse and frog PDGFs. These antisera are markedly species-specific in action. However, in radioreceptor binding assays and bioassays for mitogenic activity, human, mouse and frog PDGF AA homodimers occupy and activate murine PDGF receptors with equal efficiency.