The distribution of glycosaminoglycans in the axial region of the developing chick embryo. II. Biochemical analysis

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Abstract
An investigation of the appearance of glycosaminoglycans in the axial region (dermatome, myotome, scleratome, neural tube and notochord) of the developing chick embryo during early somite differentiation (stages 17–28; 2.5 to 5.5 days of age) was conducted with biochemical methods for comparison with a previously conducted histochemical analysis (Kvist and Finnegan, '70). The biochemical analysis confirmed that the weakly acidic anionic glycosaminoglycan observed histochemically was hyaluronic acid and that the sulphated anionic glycosaminoglycan was mainly chondroitin‐4‐ and/or chondroitin‐6‐sulphate (chondroitin‐sulphate A and/or C). Trace amounts of dermatan‐sulphate (chondroitin‐sulphate B) were found and, since some glucosamine was present in the sulphated fractions, it is possible that a small amount of heparin was present. This latter observation could account for the polysulphated material seen with histochemical methods.Quantitatively, the hyaluronic acid concentration (uronic acid/gm dry weight of tissue) was at a peak between stages 21–25 and exceeded the chondroitin‐sulphate concentration in axial tissues until stage 25, after which time chondroitin‐sulphate concentration increased very rapidly, concomitant with perichordal cartilage formation, while hyaluronic acid concentration began slowly to decline. Thus, whereas hyaluronic acid concentration was 2.5 times that of chondroitin‐sulphate at stage 17, this ratio was nearly completely reversed by stage 28.The increase in sulphated anionic glycosaminoglycans would seem to be directly related to cartilage formation but the high level of hyaluronic acid content in stages 21–25, when myotube formation as well as sclerotome aggregation are occurring, and its subsequent decrase could indicate that it plays some developmental role in somitogenesis.