Bovine nasal cartilage was extracted with inorganic salt solutions of various ionic strengths. The efficiency of extraction of protein-polysaccharide from the tissue was determined for each extraction. The results confirm and enlarge earlier observations (Sajdera & Hascall, 1969). 2. The chloride salts of lanthanide metals extract high yields of protein-polysaccharide from the tissue at much lower concentrations than was achieved with univalent and bivalent salts. 3. The lanthanum salt of extracted protein-polysaccharide precipitates when the concentration of LaCl(3) is decreased. Precipitation is complete in the presence of 0.05m-LaCl(3). This finding is relevant to the interpretation of earlier observations on the effect of LaCl(3) on elastic recovery of articular cartilage after compression (Sokoloff, 1963). 4. A linear relationship was found between the concentration at which a particular salt is maximally effective in solubilizing protein-polysaccharide from the tissue and the enthalpy of hydration of the cation of the salt. On the basis of this relationship a hypothesis is proposed to explain the characteristic protein-polysaccharide-extraction profiles exhibited by inorganic salt solutions.
