PRIOR ECCENTRIC CONTRACTIONS IMPAIR MAXIMAL INSULIN ACTION ON MUSCLE GLUCOSE-UPTAKE IN THE CONSCIOUS RAT

Our aim was to examine the effect of prior eccentric contractions on i nsulin action locally in muscle in the intact conscious rat. Anestheti zed rats performed one-leg eccentric contractions through the use of c alf muscle electrical stimulation followed by stretch of the active mu scles. Two days later, basal and euglycemic clamp studies were conduct ed with the rats in the awake fasted state. Muscle glucose metabolism was estimated from 2-[C-14(U)]deoxy-D-glucose and D-[3-H-3] glucose ad ministration, and comparisons were made between the eccentrically stim ulated and nonstimulated (control) calf muscles. At midphysiological i nsulin levels, effects of prior eccentric exercise on muscle glucose u ptake were not statistically significant. Maximal insulin stimulation revealed reduced incremental glucose uptake above basal (P < 0.05 in t he red gastrocnemius; P < 0.1 in the white gastrocnemius and soleus) a nd impaired net glycogen synthesis in all eccentrically stimulated mus cles (P < 0.05). We conclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat.