In response to insulin-like growth factor-I (IGF-I), neonatal rat cardiac myocytes exhibit a
hypertrophic response. The elucidation of the IGF-I signal transduction system in these cells
remains unknown. We show here that cardiac myocytes present a single class of high affinity
receptors (12,446±3,669 binding sites/cell) with a dissociation constant of 0.36±0.10 nm.
Two different β-subunits of IGF-I receptor were detected, and their autophosphorylation was
followed by increases in the phosphotyrosine content of extracellular signal-regulated …