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Proliferation of esophageal mucosal cells is important in repair of reflux-induced injury. We studied the effects of EGF, IGF-I, and IGF-I/binding protein-3 (BP-3) complex on immortalized esophageal epithelial (HET-1A) cells and searched for synergy between the growth factors. HET-1A cells were plated at 5 × 10⁴in 12 well plates. After 2 days in optimal media, they were maintained in basal media with or without the test peptides: EGF at 0.05–5 nM,IGF-I at 0.1–10 nM,IGF-I/BP-3 at 0.1–10 nM,and a combination of EGF at 5 nMand IGF-I or IGF-I/BP-3 at 1 and 10 nM.In comparison to basal media EGF and IGF-I stimulated cell proliferation over baseline at 5 and 10 nM,respectively. The combination of EGF at 5 nMand IGF-I at 1 and 10 nMworked synergistically, increasing cell counts over baseline to 10.3 ± 0.2 and 14.6 ± 0.8 × 10⁵, respectively. The calculated additive effect of EGF and IGF-I at 1 and 10 nMindividually …