Sulphonylureas are known to enhance insulin secretion from the pancreas and its sensitivity of the extrapancreatic target organs. In this study, we clarified a direct extrapancreatic effect of the sulphonylureas and of gliclazide, on the glucose transport system in cultured rat L6 myoblasts, which predominantly expressed glucose transporter 1 (GLUT 1). Our results show that gliclazide stimulated 2-deoxy-[3H]-D-glucose (2DG) uptake, 24 h after treatment, in a dose-dependent manner, and it also increased GLUT 1 protein synthesis and mRNA expression; 2DG uptake and GLUT 1 protein synthesis induced by gliclazide were completely blocked by protein kinase A (PKA) inhibitors (H89 and rp-cAMP), and gliclazide increased the intracellular cAMP levels 3 to 24 hr after the treatment. These results show that in rat L6 myoblasts, gliclazide stimulates glucose transport activity by the induction of GLUT 1 gene expression through PKA.