Acute growth hormone administration increases myoglobin expression and Glut4 translocation in rat cardiac muscle cells.

Oxygen (O2) and glucose are important energy sources for the heart. This study sought to investigate the effects of acute growth hormone (GH) administration on the expression of myoglobin (Mb) and Glut4 glucose transporter, two important limiting factors for O2 and glucose utilization for energy production, in cardiac muscle cells of treated rats. Male Wistar rats were sacrificed at 30, 45, 90 and 120 min after a single dose of intraperitoneal (ip) rat GH (1.5 mg/kg) or vehicle administration, and total RNA and protein (from whole cell or subcellular fractions) were extracted from cardiomyocytes (left ventricles) of these animals. Acute GH injection led to a significant increase in both Mb mRNA and protein levels, and stimulated Glut4 protein translocation to the plasma membrane of cardiac cells. These results suggest that GH exerts some of its effects on cardiomyocytes shortly after the first administration inducing the expression of proteins potentially involved in cardiac performance.