A HISTOCHEMICAL-STUDY OF ANIONIC SITES IN THE INTERMEDIATE LAYER OF RAT FEMORAL CARTILAGE USING POLYETHYLENEIMINE AT DIFFERENT PH LEVELS

Anionic sites in the intermediate layer of young rat hyaline cartilage s were examined using a cationic dye, polyethyleneimine (PEI), at diff erent pH levels. Femoral heads were resected and fixed in 2.5% glutara ldehyde and treated with 0.5% PEI at pH 7.4, pH 2.5 or pH 1.0. Some ca rtilage samples were first digested with chondroitinase ABC or hyaluro nidase. The PEI deposits at pH 7.4 appeared to be irregular shapes. Th eir sizes seemed to be larger than those at pH 2.5 or pH 1.0. The PEI deposits were also found on the surface of collagen fibrils at both pH 7.4 and pH 2.5 even after the chondroitinase ABC digestion, but were not found at pH 1.0. Moreover, they disappeared after hyaluronidase di gestion. Accordingly, it is suggested that PEI-positive structures var ied depending on pH levels. In addition, hyaluronan may be localized n ear collagen fibrils, but most sulphated proteoglycans may not.