Platelet-derived growth factor-BB (PDGF-BB) is a homodimeric isoform of the PDGF family of growth factors that plays a crucial role in regulating cell proliferation, migration, and survival. In rats, PDGF-BB is produced by various cell types, including platelets, endothelial cells, and smooth muscle cells, and acts on cells expressing PDGF receptors, such as PDGFR-α and PDGFR-β. Upon binding to its receptors, PDGF-BB activates intracellular signaling pathways, such as the Ras-MAPK and PI3K-Akt pathways, leading to cellular responses involved in tissue repair, angiogenesis, and fibrosis. PDGF-BB is known for its mitogenic and chemotactic effects on mesenchymal cells, including fibroblasts and smooth muscle cells, and plays a critical role in wound healing, tissue remodeling, and vascular development.