Localization of the insulin-like growth factor system in a rat model of heart failure induced by myocardial infarction

Although cardiac effects of growth hormone (GH) and insulin-like growth factor (IGF)-I have been reported in experimental models of heart failure and in human dilated cardiomyopathy, the ICF system has not been comprehensively assessed in the failing heart. We therefore localized the IGF system in the left ventricle during congestive heart failure after myocardial infarction (MI) in the rat. The left anterior descending coronary artery was ligated in adult female Sprague-Dawley rats and hearts were examined after 6 months when congestive heart failure had developed. In situ hybridization histochemistry was used to localize mRNA for the components of the IGF system in the left ventricle of sham and congestive heart failure animals. We were able to detect changes in the spatial distribution of mRNA for ICF-I and IGF binding proteins 3, 4, 5, and 6 in the left ventricle during congestive heart failure after MI. IGF-I and the binding proteins were predominantly increased in the iniarct/peri-infarct area of the left ventricle. Other components of the ICF system were indistinguishable from the low to undetectable levels in sham-operated rats. These results demonstrate that the IGF system is altered in the failing heart and suggest that the IGF system plays an important role in the response of the heart to MI and consequent failure.