Effect of Vitamin a Deficiency on Calcium and Glycosaminoglycan Metabolism in Guinea Pig Bone

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Abstract
Using a standardized guinea pig model system, the effect of vitamin A deficiency on new bone formation was investigated. Guinea pigs were fed a purified gel diet with vitamin A (28.5 mg/kg) or without it (A-). The onset of deficiency was determined by a decrease in the serum vitamin A concentrations of the A- guinea pigs. The right incisor was then extracted from each animal and a 1 cm tube implanted in the alveolar cavity. Half of the number of guinea pigs in the A- group were fed retinoic acid (A-/A+; 1 µg/day). The controls (A+) and those receiving retinoic acid (A-/A+) were pair-fed to the A- group. Fourteen days after implantation, the guinea pigs were killed and the nylon tubes filled with new bone (tissue implants, TI) were removed and placed in a tissue culture system in the presence of 45Ca or 35SO4 for 48 hours. The total calcium content of the A- TI was significantly lower than the A+ TI and the uptake of 45Ca seemed to be less in the A- TI compared to the other two groups. The glycosaminoglycan (GAG) fraction from the A- and A-/A+ TI cultured with 35SO4 contained significantly more 35S-sulfur than did the same fraction from the A+ TI. Thus, the lack of dietary vitamin A increased the amount of sulfur present in the glycosaminoglycan fraction, possibly indicating an increase in the amount of sulfated glycosaminoglycans present.