الفهرس 
Epiphyseal plate of long bonesOnly 14 pages are availabe for public view
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Abstract
Vitamin A is a fat soluble vitamin. Some individuals receive more than the recommended daily allowance of vitamin A due to dietary habits or use of dietary supplements that contain vitamin A. This study aimed to investigate the effects of vitamin A overdose on the epiphyseal plate structure in young rats and on the structure of the metaphysis of adult rats.
Materials and methods: Seventy male albino rats were divided into two main groups. Group I (young group) consisted of 40 rats -four weeks old- that were subdivided into four equal subgroups. Subgroup (Ia) was used as control. Rats of subgroups Ib, Ic and Id were given vitamin A at a dose of 100000 IU/100 gm/day for five days. These rats were sacrificed at the sixth, eighth and twelfths day from the beginning of the experiment respectively. Group II (adult group) consisted of 30 adult rats that were subdivided into three equal subgroups. Subgroup (IIa) was used as control. Rats of subgroup IIb and IIc were given vitamin A at a dose of 80 mg/kg/day for two weeks (group IIb) and three weeks (group IIc). Animal were sacrificed at the end of these two and three weeks respectively. The proximal ends of tibiae of the hind limbs were taken, processed and examined by light and scanning electron microscopes. Morphometric and statistical studies were also done.
Results: Vitamin A overdose had significant and progressive serious effects on epiphyseal plate in young rats and on cancellous bone structure in metaphysis of adult rats.
Conclusion: Vitamin A overdose proved to be toxic as it induced premature closure of epiphysis in young rats and osteoporosis in adult rats.