Keratan sulfate is a component of proteoglycans in the compressed region of adult bovine flexor tendon

Abstract

A monoclonal antibody (ET-4-A-4) was used to identify keratan sulfate (KS) as a constituent of bovine flexor tendon. KS was present in at least 500-fold higher amounts in the fibrocartilaginous region of the tendon that is subjected to compressive forces in vivo (mean = 0.03% of tissue dry weight) than in the more proximal regions subjected only to tensional forces. The KS was associated with proteoglycans of three size categories that could be separated by Sepharose CL-4B chromatography. The largest proteoglycan (Vo) contained approximately 4% KS and was predominant in the surface region of the tendon subjected directly to compressive forces. A population of somewhat smaller molecules (Kav approximately equal to 0.3) contained less than or equal to 20% KS and proportionately less chondroitin sulfate (CS) or dermatan sulfate (DS). The KS chains of this population were not digested by keratanase. This population was dominant in tissue from the middle layer of the fibrocartilaginous region. A third population of small KS proteoglycans or fragments (Kav approximately equal to 0.6) comprised 40% of the KS found in the deepest layer of the compressed tendon region. This smaller component was independent of the small DS proteoglycans.