Papain-induced changes in intracellular lipid levels in cartilage

Loss of proteoglycans from the cartilage matrix of the ears of young rabbits was induced by intravenous injection of papain so as to permit histochemical observation of lipid levels in chondrocytes during both the depletion process and subsequent proteoglycan synthesis by the chondrocytes. Lipid content was quantified using an image analyser. Between 4 and 24 h after injection, loss of proteoglycans was accompanied by a fall in intracellular fat levels. In the 24- to 120-hour post-injection period, matrix proteoglycan levels and basophilia recovered parallel to the intracellular fat content. The function of intracellular lipids in cartilage is discussed in the light of these results.