[Experimental study of hyperostosis induced by hypervitaminosis A]

Radiological and histological studies were made on retinoid-induced hyperostosis in rats. Vitamin A (VA) was administered intraperitoneally in rats for 6 months. Hyperostosis was observed in 94 percent of rats administered VA and in 38 percent of the control. Chondrocytes and vascular proliferation were observed in the attachment of the tendons and in the anterior corner of the vertebral body after 3 months. Hyperostosis was observed as osteophytes in the attachment of ligaments or tendons and as heterotopic ossification in the tendons or the joint capsules of the whole body after 6 months. Immature cells were observed around the osteophytes. These areas were stained with pH 4.1 toluidine blue and disappeared following streptomyces hyaluronidase treatment. This would indicate that hyaluronic acid increased around these areas. These results appear to demonstrate that hypervitaminosis A is capable of producing hyperostosis.