INSULIN-LIKE GROWTH FACTOR I RECEPTORS IN HUMAN CARDIAC MYOCYTES AND THEIR RELATION TO MYOCARDIAL HYPERTROPHY

Specific binding sites for insulin-like growth factor I (IGF-I) and their expression during cardiac myocyte hypertrophy were studied by autoradiographic analysis of right ventricular biopsy specimens from patients with hypertrophic cardiomyopathy (9 cases), dilated cardiomyopathy (8 cases), and sick sinus syndrome (5 cases). Frozen specimens were cut into 5 /μm-thick sections and thaw-mounted on albumin-coated slides. After incubation with [125I]IGF-I, with or without excess cold IGF-I, autoradiography was performed, and grains over myocytes were counted microscopically. Binding of [125I]IGF-I was inhibited in a dose-dependent manner by unlabeled IGF-I and competed for by IGF-I > IGF-II>insulin. The maximal grain density was higher in hypertrophic cardiomyopathy (186±47/1.8×10-2 mm2) than in dilated cardiomyopathy (124±13/1.8×10-2 mm2) or sick sinus syndrome (98±18/1.8×10-2 mm2) (p