Abstract des Autors

The aim of the present study was to examine the rate of glycogen mobilization during exercise and the rate of the postexercise glycogen replenishment in different muscle types (white (WG), and red (RG) gastrocnemius, soleus (S) and diaphragm (D)) in rats treated with triiodothyronine (T3, group T). Rats of the control group (C) were treated with saline. The animals were made to run on a treadmill set at 0ø gradient and at a speed of 1200 m/h. The time taken to reach exhaustion in group C was 188(SD 23) min, whereas in group T, it was only 63(SD 12) min. The content of glycogen in all muscles of the rats from group T at rest and during exercise was significantly lower than in group C at each corresponding time. At exhaustion, the glycogen content was in WG(C) 34.79(SD 4.65), (T) 20.10(SD 4.10); in RG(C) 22.82(SD 4.66), (T) 16.50(SD 2.00); in S(C) 14.85(SD 2.48), (T) 11.90(SD 2.93); in D(C) 18.18(SD 3.49), (T) 7.54(SD 3.36) (micro-mol of glucosyl units/g). The amount of glycogen mobilized during exhausting exercise in RG, S and D was similar in both groups whereas in WG it was much higher in rats of group T than in group C. The concentration of glycogen returned to pre-exercise values in each muscle 3 h after exercise. The net amount of glycogen resynthetized during 3 h of recovery depended on the muscle type. It was in WG(C) 3.30, (T) 18.03; in RG(C) 21.34, (T) 25.88, in S(C) 34.00, (T) 17.68, and in D(C) 17.25, (T) 12.22 micro-mol of glucosyl units/g (each number represents the difference between the means). It concluded that treatment with T3 markedly affects this exercise-induced metabolism of glycogen in each muscle type. From our study it is suggested that low muscle glycogen content may contribute to a reduction in exercise performance in hyperthyroidism. Verf.-Referat