GS activity ratio in glucose-replete and -depleted cells. Cultured human myotubes were transduced with Ad-GFP, Ad-R6, Ad-PTG or Ad-G_M and then incubated with (white columns) or without (black columns) 25 mM glucose for 24 h. GS activity ratio (without glucose 6-phosphate/with glucose 6-phosphate) was measured in cell extracts. Data are means ± SEM from five experiments performed in duplicate. Significance of differences: versus cells treated with Ad-GFP under the same incubation conditions, *p < 0.05 and **p < 0.0001; cells without glucose versus with glucose for any viral treatment, †p < 0.01 and ‡p < 0.0001.