IMMUNOHISTOCHEMICAL STUDY OF A CHONDROITIN-6-SULFATE IN GROWTH PLATESOF BROILER-CHICKENS WITH HIGH AND LOW GENETIC PREDISPOSITIONS TO TIBIAL DYSCHONDROPLASIA

The distribution of a chondroitin-6-sulfate (C6S) epitope, which is a biochemical marker of chondrocyte hypertrophy, was studied in the grow th plates of two lines of 3-week-old broiler chickens with low and hig h genetic predispositions to tibial dyschondroplasia (TD). Ultrathin s ections of growth plates from both groups were subjected to immunoloca lization with monoclonal antibody 3-B-3(-), the epitope of which is in creased on proteoglycans made by hypertrophic chondrocytes. Bound anti body was localized with colloidal gold-labeled protein A for observati on with an electron microscope. The 3-B-3(-) epitope was localized in pericellular and interterritorial matrix of growth plates of both line s. In the low-TD-incidence birds, the concentration of 3-B-3(-) bound to CGS progressively increased from the proliferative zone co the hype rtrophic zone. However, in the high-TD-incidence line, the epitope exp ression remained at a low level in all zones. The increase of the 3-B- 3(-) epitope produced by maturing growth-plate chondrocytes is indicat ive of changes in the glycosaminoglycan chains of proteoglycans that m ay be important in the process of matrical calcification. Thus, failur e of chondrocytes of the high-TD-incidence line to produce this change in post-translational modification of their proteoglycans could be im portant in the pathological process.