Effect of Zinc and Exercise on Enchondral Ossification of Rats

Objectives: To observe the effect of zinc combined with moderate exercise on the ultrastructure alteration of enchondral ossification in tibial metaphysis of growing rats. Methods: Twenty-five 4-week-old male Wistar rats were divided randomly into five groups. In control group, rats were not manipulated and fed on standard diet alone. The experimental groups were fed on a high-zinc diet, standard diet, low-zinc diet and zinc deficient diet, respectively. And the rats were exercised on a flat-bed treadmill, the exercise consisted of 1 hour per day, 5 days a week for 4 weeks and the speed of it was 12m/minute. The tibiae were harvested after five weeks then we examined the ultrastructure alterations in tibial metaphysis by using scanning electron microscope (SEM) and transmission electron microscope (TEM). Results: In the zinc deficient diet exercise (DE) group, the layers of cartilage and the outline of the chondrocytic lacuna were indistinct, sparser calcospherites were commonly seen. The characteristic of the low zinc diet exercise (LE) group was there were more Howship's lacuna than that of the SE group and the control group. More distinct calcospherites, regularly arranged collagen fibers and thicker traceular were seen in the high zinc diet exercise (HE) group. The TEM investigation showed thicker osteoid and more osteoblasts than that of control group were seen in the SE group. The number of osteoblast and osteoclast decreased in the DE group and most of them were inactive. The image of the LE group was similar to the control group except that more active osteoclasts increased in number were found. More active osteoblasts and young osteocytes were commonly seen in the HE group, the thickness of osteoid was thicker than that of the SE group. Conclusion: These findings suggested zinc combined with moderate exercise have beneficial effects on enchondral ossification in growing rats.