Contraction-stimulated muscle glucose transport and GLUT-4 surface contentare dependent on glycogen content

The influence of muscle glycogen content on basal and contraction-induced g lucose transport and cell surface GLUT-4 content was studied in rat skeleta l muscle. Wistar rats were preconditioned by a combination of swimming exer cise and diet, resulting in 40% lower (LG) or threefold higher (HG) muscle glycogen content compared with nonexercised controls (NG). At rest and duri ng contractions, S-deoxy-D-glucose uptake in perfused fast-twitch muscle, b ut not slow-twitch muscle, was significantly lower in HG compared with LG. Cell surface GLUT-4 content in the fast-twitch plantaris was 994 +/- 180, 1 ,173 +/- 311, and 2,155 +/- 243 dpm/g in the basal condition and increased (P < 0.05) to 2,285 +/- 239, 3,230 +/- 464, and 4,847 +/- 654 dpm/g during contractions with HG, NG, and LG, respectively, the increase being signific antly smaller in HG compared with LG. The contraction-induced increments in glucose transport and in cell surface GLUT-4 content were negatively corre lated with the initial glycogen content (P < 0.01). In conclusion, glucose transport and cell surface GLUT-4 content in resting and contracting fast-t witch muscle are dependent on the muscle glycogen content.