Chondrodysplasia in the Alaskan malamute. Characterization of proteoglycans dissociatively extracted from dwarf growth plates.

Proteoglycan monomers obtained from the dissociative extraction of growth plate cartilages of chondrodysplastic and homozygous nonaffected Alaskan malamute dogs were characterized with regard to hydrodynamic size and glycosaminoglycan composition. Dissociative extraction solubilized 91.7% of the uronic acid and 71.7% of the protein from dwarf growth plates compared to 76.8% of the uronic acid and 50.2% of the protein from normal growth plates. Dissociative density gradient ultracentrifugation of the extracts resulted in the recovery of 84% of the uronic acid from dwarf growth plates and 71% of the uronic acid from normal growth plates in the D1 fraction. High-pressure liquid chromatography of the dwarf D1 monomers revealed a single peak with a retention time of 8.6 minutes while the normal D1 monomers eluted later with a retention time of 8.9 minutes. After reduction of the dwarf D1 monomers, the chondroitin sulfate side chains eluted from Sepharose CL-6B with an approximate molecular weight of 15,000 (Kav of 0.55) while those from the normal eluted with an estimated molecular weight of 9,500 (Kav of 0.64). High-pressure liquid chromatography analysis of the unsaturated disaccharides from the dwarf D1 fractions revealed increased amounts of chondroitin-6-sulfate. Analysis of the fractions for glucosamine and galactosamine revealed that dwarf D1 and D2 fractions were enriched in galactosamine. These findings indicate that the extracellular matrices of dwarf growth plates contain proteoglycan monomers which may be indicative of a less mature extracellular cartilage matrix than the cartilage matrices of age-matched normal dogs.