Effects of voluntary exercise on bone growth and calcium metabolism in spontaneously hypertensive rats

The effects of voluntary exercise on bone length and calcium metabolism were investigated in spontaneously hypertensive rats (SHR) and Wistar rats. They were classified into voluntary exercise or sedentary group. Systolic blood pressure (SBP), bone length, urinary calcium excretion, plasma calcium and parathyroid hormone levels (PTH) were measured for analysis. SBP of the trained SHR (T-SHR) was significantly lower than that of the nontrained SHR (NT-SHR) at 10 and 11 weeks of age, but the trained Wistar rats (T-WR) and the nontrained Wistar rats (NT-WR) had similar SBP throughout the experimental period. The T-SHR had significantly longer bones in the extremities and the trunk than the NT-SHR, whereas the T-WR had similar or shorter bones than the NT-WR. The PTH level at 12 weeks of age was significantly lower in the T-SHR than in the NT-SHR. The urinary calcium excretion of the T-SHR was greater than that of the NT-SHR, but the food intake (calcium intake) of the T-SHR was also greater. The urinary calcium excretion and food intake of the T-WR and NT-WR were similar. No noticeable differences were observed in the plasma calcium level between the T-SHR and NT-SHR, the T-WR and NT-WR. From these results it is suggested that the abnormal calcium metabolism in the SHR is improved in some degree by voluntary exercise.