|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥1,700,000 (Direct Cost : ¥1,700,000)
The rehabilitating effects of voluntary running on muscle atrophy due to a low protein diet were studied in rat muscle. Female weanling rats were randomly assigned to four experimental gouts : sedentary control on standard protein diet(SP/C), exercising on SP diet(SP/E), sedentary control on low protein diet (LP/C), exercising on LP diet(LP/E). Rats were allowed ad libitum access food and water. Exercising rats were placed in steel cages free access to running wheels from the beginning. Low protein diet replaced SP diet in LP groups on 7 weeks of age. Three weeks later, gastrocnemius, soleus(SOL), extensor digitorum longus(EDL) muscles were dissected and weighed. Fiber number of muscle was counted through profile projector under a dissecting microscope after nitric acid treatment. Fiber area was measured by an image processing system. Fiber composition (typesI, IIA, IIB) was determined with the myosin ATPase method after pre incubation at 10.8, 4.5, and 4.3.
Low protein intake, producin
g a loss of body-weight, caused a significant weight loss of heart and skeletal muscles. Although running activity of LP/E group was lowered to 1/3-1/2 of that of SP/E group, exercise still increased muscle weights significantly and was effective in recovery of weight of skeletal muscles. Protein deficiency reduced the muscle weight due to the decrease of number and size in muscle fibers, especially in type 1. However, the reductions of fiber size and number were inhibited by exercise and the muscle weight was restored to control level. The recovery of fiber number and size was largely due to that of type I.Thus, predominantly type I SOL responded to low protein intake and exercise rather than predominantly type II EDL.
It was concluded that the decrease in number and area of muscle fibers during low protein intake was inhibited by running exercise and the muscle can be restored to normal. These results suggested that exercise may be an essential factor for adaptive mechanism to protein deficiency in Papua New Guinea highlanders, whose physique was very muscular in spite of low protein intake. Less