THE FINE STRUCTURE OF BOVINE NASAL CARTILAGE Extraction as a Technique to Study Proteoglycans and Collagen in Cartilage Matrix

Bovine nasal cartilage was studied by electron microscopy before and after extraction with 4 M guanidinium chloride or 1 .9 M CaC12. These solvents removed matrix granules, basophilia, and 85% of the proteoglycan complex, measured as hexuronate . Simultaneously, many collagen fibrils were disaggregated into component microfibrils (approximately 40 A thick) . In contrast to the above solvents, exhaustive extraction with 0 .5 M guanidinium chloride removed 20% of the proteoglycan complex, and matrix granules were reduced in size but not in number . Extraction with 4 M CaC12 removed only 10% of the proteoglycan complex, did not remove matrix granules, and caused the normal banding pattern of collagen to disappear . The banding was restored by further treatment with trypsin . Trypsin, before or after 4 M CaC12, removed matrix granules and 90% of the proteoglycan complex . We conclude that matrix granules are an electron microscopic representation of the proteoglycan complex, and consist of more than one proteoglycan macromolecule . It would appear that 4 M guanidinium chloride and 1 .9 M CaC12, in addition to removing most of the proteoglycan complex, also disaggregate some of the collagen fibrils into their component microfibrils.