The effect of vitamin D on the beryllium rickets of the rat incisor

Abstract

This report is based on the histologic and chemical study of the effect of beryllium carbonate (6 per cent) in a synthetic diet given weaned rats of the Sprague-Dawley strain for periods of fourteen to 168 days. One group of twenty animals was given the physiologic requirement of vitamin D, and another group of twenty animals was given an excess but not toxic dose. Thirty-nine littermates were pair-fed as controls. The following results were observed: 1. 1. Beryllium was found in the feces but not in any of the organs or the incisor. 2. 2. The blood level of phosphorus fell to an average of 2 mg. per cent in the beryllium-carbonate-fed rats on physiologic doses of vitamin D. The phosphorus levels gradually increased despite continued experimental feeding and averaged 5 mg. per cent in animals 192 days old. 3. 3. The blood phosphorus levels were normal in the animals on high doses of vitamin D. 4. 4. The blood calcium levels were normal in all animals. 5. 5. The epiphyseal plate of the tibia was increased in width in rats fed physiologic doses of vitamin D and was of normal width in animals fed high doses of vitamin D. 6. 6. The changes in the incisor and its supporting tissues indicate severe rickets in the animals on physiologic vitamin D and mild rickets in the animals on an excess dose of vitamin D. The severe rachitic syndrome consisted of enamel hypoplasia and aplasia, severe retardation in the formation and calcification of dentine, failure of newly formed bone tissue to calcify, and resistance of such bone tissue to resorption. These changes were progressive up to approximately the seventieth day of the experiment. Partial recovery occurred in older animals. Secondary to the resistance to resorption of uncalcified bone, there were narrowing and obliteration of the periodontal space, arrest in eruption of the incisor, folding of the odontogenic epithelium, enamel, and dentine, and pulpal obliteration due to continued dentine apposition. In the mild form of beryllium rickets, the disease was confined to animals under 3 months of age and to the following symptoms: the rate of dentine apposition was slightly retarded and calcification of lingual dentine was impaired. The alveolar bone showed only a slightly widened osteoid seam.