Effect of hypervitaminoisis A on composition of chick cartilage

1. Day-old chicks were fed a diet containing one mg of retinyl acetate per kg feed. One group was treated with 18.300 mug retinyl acetate/100 g of body weight/week, whereas the other group served as control. Retinol treatment did not affect weight gain during a 4-weeks observation period. 2. At the end of this period the animals were killed and epiphyseal cartilage of the tibiotarsus examined. Retinol excess decreased ash and hydroxyproline and increased glycosaminoglycans and uronic acid in dry, fat-free cartilage. Sialic acid and hexosamine contents of glycosaminoglycans were elevated without a great change in the proportion of glucosamine and galactosamine. 3. Activity of 5 enzymes degrading glycosaminoglycans was not affected by retinol excess. 4. In hypervitaminotic chicks, uptake of injected radiosulphate by cartilage tissue and incorporation into glycosaminoglycans were enhanced and breakdown retarded.