Activity of human, bovine and porcine platelet-derived growth factor in a radioreceptor assay with human placental membrane protein.

Radioiodinated human platelet-derived growth factor (125I-PDGF), and unlabeled human (Hu), bovine (Bo), and porcine (Po) PDGF were used to study PDGF receptors in human term placental membrane preparations. The binding of 125I-Hu-PDGF was inhibited by unlabeled preparations. Half-maximal occupancy of the binding sites occurred at 7-9 nM of Hu-, Bo- or Po-PDGF. Scatchard analysis of the binding data indicated a single class of receptors having a Kd value of about 1.1-1.2 X 10(-10) M. Thus, the sensitive radioreceptor assay does not detect any species specificity of PDGF.