Summary

The dorsal skin of the chick embryo, in which feather germ forms, was found to synthesize two proteochondroitin sulphates, PCS-I and PCS-II and a proteoheparan sulphate, PHS. A monoclonal antibody (I3B9) was prepared against PCS-I, a higher molecular weight proteochondroitin sulphate. Distribution of PCS-I was immunohistochemically studied using I3B9. PCS-I was found in the epidermis, basement membrane and superficial dermis prior to formation of feather rudiments. As the feather rudiments formed, PCS-I was noted in a condensed area of dermal cells and in the basement membrane, while PCS-I decreased remarkably in the epidermal placode. The formation of feather buds resulted in a decrease in PCS-I in the region of dermal condensation and the basement membrane situated above this region. PCS-I was asymmetrically distributed in the feather filaments. The turnover of proteochondroitin sulphate was studied using autoradiography of [³⁵S]sulphate. Proteochondroitin sulphate in the basement membrane and condensed dermis of the feather rudiments showed very slow turnover. On the other hand, the outgrowth of feather buds caused rapid turnover of proteochondroitin sulphate in the region of dermal condensation and basement membrane situated above this region. The mechanism for the uneven distribution of PCS-I during feather germ formation is discussed.