Differential Cardiac Effects of Growth Hormone and Insulin-like Growth Factor1 in the Rat

Abstract

Background Despite their increasing clinical use and recent evidence that growth hormone (GH) and insulin-like growth factor–1 (IGF-1) target the heart, there has been no systematic investigation of the effects of GH and IGF-1 on the cardiovascular system. Methods and Results Sixty normal but growing adult female rats were randomized to receive 4 weeks of treatment with GH (3.5 mg · kg−1 · d−1), IGF-1 (3 mg · kg−1 · d−1), a combination of the two, or placebo. Transthoracic echocardiograms were performed at baseline and at 2 weeks and 4 weeks of treatment. After the final echocardiography, rats underwent either closed-chest left ventricular (LV) catheterization or Langendorff perfusion studies. Myocyte diameter and interstitial tissue fraction were assessed by morphometric histology. Echocardiographic and ex vivo data demonstrated a LV hypertrophic response in all three groups of treated animals that was most marked in the GH group, which alone exhibited a concentric growth pattern (relative wall thickness...