PLEIOTROPHIN IS AN ABUNDANT PROTEIN IN DISSOCIATIVE EXTRACTS OF BOVINE FETAL EPIPHYSEAL CARTILAGE AND NASAL CARTILAGE FROM NEWBORNS

An abundant protein that is identical to the growth-associated protein pleiotrophin (PTN) has been isolated from dissociative extracts of bo vine nasal and fetal epiphyseal cartilage. The yield from these tissue s was at least 15 mug/g wet weight of cartilage. PTN was absent or was present only in trace amounts in mature articular cartilage. An analy sis of tryptic fragments of PTN, held together with disulfide bonds, d id not indicate any set pattern of cystine cross-links, which suggests a propensity for rapid refolding of the protein. PTN could not be iso lated from thin (10 mum) slices of nasal cartilage in physiological ex traction buffers, which indicates that it was tightly associated with the cell surface, was tightly associated with nonextractable matrix, o r was an intracellular protein. Its appearance in various extraction m edia parallels that of histone H2b, a nucleosomal protein; this sugges ts a possible intracellular location for the protein. Immunohistochemi cal analysis of its distribution in fetal epiphysis indicated that it is associated with chondrocytes.