Collagen content of blood vessels has been used to evaluate the progression of arteriosclerosis. We examined the effect of chronic physical exercise on aortic collagen content in the Spontaneously Hypertensive Rats (SHR).
　Ten week old animals were trained either by forced treadmill running (26.8 m/min-1 hr/day) or voluntary exercise in running wheels @7,800 m/day at peak) for 8 weeks. Succinate dehydrogenase (SDH) activity of the soleus muscle for forced exercised animals was 13% greater (p<0.01) than that of sedentary animals (6.56±0.17 μmoles/g/min; mean±SEM), whereas soleus SDH activity for voluntarily exercised group was the same as that of sedentary group.
　The blood pressure increased 15, 12 and 20% for the sedentary, voluntarily, and forced exercised groups, respectively during the training period. There was significant difference in the increment of the blood pressure (p<0.05) between voluntarily and forced exercised groups.
　Total protein content (@250 mg/g tissue) were no measurable change by training program. The aortic collagen contents of voluntarily trained group (96.5±2.0 mg/g tissue, 39.8±0.7 mg/100mg protein) were significantly (p<0.05) less than those of forced trained group.
　The results of these experiments indicate that chronic physical training altered aortic collagen synthesis in the SHR rats．We concluded that chronic voluntary exercise results in the depression of systolic blood pressure in the SHR rats, which may be associated with lesser synthesis of artery collagen.

DESCENTE SPORTS SCIENCE Vol.3/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE