Although insulin resistance in peripheral tissue has been demonstrated in patients with cardiac disease, expression of glucose transporter (GLUT) isoform mRNA in the cardiac muscle is not known. We analyzed GLUT isoform mRNA in the cardiac muscle of 10 patients by RT-PCR. GLUT 4 mRNA was semi-quantitated by kinetic analysis, altering the cycles of PCR, and insulin resistance was examined by euglycemic hyperinsulinemic glucose clamp with an artificial pancreas. In addition to GLUT 2, 3, and 4 mRNA, all of which were constantly demonstrated in the skeletal muscle of normal volunteers, GLUT 1 was documented in all the cardiac samples examined. The quantity of GLUT4 mRNA was not related to the degree of insulin resistance or M values. These results may suggest that glucose uptake in the cardiac muscle is maintained by 4 different glucose transporters and that the response of GLUT 4 mRNA to insulin resistance is different in the cardiac muscle and in the skeletal muscle.