Acute exercise induces mitochondrial swelling of hepatocytes surrounding the terminal hepatic venule in rat liver acinus / 体力科学

In this study, we investigated the effect of acute exercise on the mitochondrial structure of hepatocytes surrounding the terminal hepatic venule (zone III) in the rat liver acinus. Male SD rats were assigned to a resting group (n=8) and to running groups ran on a motor-driven treadmill for 100 min (n = 8) or did continued running beyond 100 min until exhaustion (n = 5) . Plasma guanase activity was increased with duration time of exercise. The arterial ketone body rate (AKBR) increased during the 100 min of running, but the AKBR significantly diminished with exhaustive running as compared with that for 100 min of running. Although there was no change in the mitochondrial structure of hepatocytes in the perportal area (zone I) during exhaustion, remarkable swelling was observed in that in zone III.<BR>These results suggest that acute running affects mitochondrial structures in zone III, and that this might be a hypoxia zone during exercise.

Effect of hyperglycemia on glycogen repletion after skeletal muscle contraction / 体力科学

Previous studies of the effect of exercise on glucose metabolism in diabetes mellitus have focused on the stimulation of glucose disposal capacity by insulin and muscle contraction. We have investigated the effects of hyperglycemia on the increase in muscle glycogen after exercise and the role of physiological saline (saline) injection under hyperglycemic conditions. Male Wistar rats weighing 100-150g (n=52) were made diabetic (DM) by injection of 90 mg/kg streptozotocin (STZ) . Glycogen content was reduced by in situ electrical stimulation of the sciatic nerve. Immediately after stimulation, the rats were injected with glucose or saline. After a 20 min recovery period, the glycogen content of the white and red gastrocnemius (WG, RG), soleus (SOL), plantaris (PL), extensor digitorum longus (EDL) and tibialis anterior (TA) was significantly increased by glucose injection in the control rats. In DM rats, the glycogen content of the TA and EDL was increased, whereas there was no change in the WG, RG, SOL and PL. These results suggest that, in hyperglycemic rats, muscle glycogen resynthesis in only fast-twitch fibers is increased by muscle contraction. However, after injection of saline, the plasma osmolality decreases significantly and glycogen resynthesis by all muscles except the SOL in diabetic rats is improved, although there is no significant increase in control rats. It is concluded that glycogenolysis and resynthesis after muscle contraction are reduced by hyperglycemia. The data suggest a possible role of saline injection in the development of glycogen resynthesis in hyperglycemia.