Insulin-like growth factor I and II preserve myocardial structure in postinfarct swine

Background-Insulin-like growth factors (IGF) I and II improve myocardial fu nction after coronary occlusion in different animal models. Objectives-To investigate the mechanism of improved myocardial function aft er administration of IGF-I or IGF-II in acute myocardial infarction. Methods-Female pigs (mean (SD) weight 25 (5) kg) were subjected to acute my ocardial infarction by microembolisation with 75-150 mum affigel blue beads . The beads contained and slowly released 150 mug/pig of IGF-I (n = 6), IGF -II (n = 6), or pig albumin (n = 6). Echocardiography, perfusion imaging, a nd haemodynamic measurements were performed before infarction and during fo ur weeks after infarction. Regional wall motion of different left ventricul ar segments was scored semiquantitatively on the basis of a three point sco ring system, from normal = 0 to dyskinesia = 3. Serum cardiac troponin I co ncentration was measured before, immediately after, and three hours after t he infarct. Excised hearts were analysed for actin, desmin, blood vessel de nsity and DNA laddering within the infarct, border, and normal myocardial a reas. Results-Myocardial function of the infarct related area improved significan tly during the four weeks of follow up in both the IGF groups (p = 0.01). M yocardial perfusion, heart rate, and blood pressure were similar in all the animals during the study. Treated animals had lower serum cardiac troponin I concentration (p = 0.001), more actin in the border area (p = 0.01) and infarct area (p = 0.0001), and reduced DNA laddering in the infarct area co mpared with the controls (p < 0.05). IGF groups had more blood vessels in t he border area (p = 0.04) and the infarct area (p = 0.003). Conclusions-Both types of IGF improved myocardial function and the improvem ent was associated with preservation of myocardial structure. IGF-I was mor e effective than IGF-II.