Rat Platelet-Derived Growth Factor-BB (PDGF-BB) is a homodimeric growth factor composed of two PDGF-B chains that regulates cell proliferation, migration, angiogenesis, and tissue repair in rats (Rattus norvegicus). PDGF-BB signals primarily through platelet-derived growth factor receptor-β (PDGFR-β) and PDGFR-α/β receptor complexes, activating downstream signaling pathways including PI3K/AKT, MAPK, and STAT, which control fibroblast activation, smooth muscle cell proliferation, and extracellular matrix production. In rats, PDGF-BB is produced by platelets, macrophages, endothelial cells, fibroblasts, and other stromal cells, and is released during tissue injury, inflammation, and wound healing. Rat PDGF-BB is extensively studied in experimental models of cardiovascular disease, fibrosis, wound healing, and cancer, where PDGF signaling contributes to vascular smooth muscle cell proliferation, angiogenesis, and tissue remodeling. It plays key roles in rat models of atherosclerosis, kidney fibrosis, liver injury, and vascular restenosis, where PDGF-driven signaling influences inflammatory responses and extracellular matrix deposition. Because rats are widely used in pharmacology, toxicology, and cardiovascular research, characterization of rat PDGF-BB supports investigations into growth factor signaling, vascular remodeling, and regenerative processes relevant to human disease and therapeutic development.