Histochemical Studies of Chondrocyte Function in the Cartilage 



43 



Acid phosphatase appeared in increasing amounts in the maturing chondrocytes of 

 the hypertrophic zone up to the point of commencing mineralisation. Surviving 

 chondrocytes in the mineralising cartilage showed a lower level of activity (Fig. 2). 



|*>* ^ 



Fig. 4. Serial section to Fig. 3 showmi; ,i 

 sent in the chondrocytes but has disappc 



GUcogen (arrow) is pre- 

 ection post-fi.xed in 90% 



cohol'tormalin. 



Non-specific esterase activity was present in the same distribution as acid phos- 

 phatase and showed as small positive granules in the chondrocyte cytoplasm. Similar 

 granules were seen in the acid phosphatase preparations. These observations indicate 

 the presence of lysosomes in the chondrocytes which would be in accord with recent 

 views on the mechanism of cartilage resorbtion (Fell, 1964; Sledge and Dingle, 

 1965). On the other hand the chondrocytes in the mineralising zone are probably 

 dying cells so it is possible that the acid hydrolase positive bodies could represent 

 autophagic vacuoles (de Duve, 1963). 



Alkaline phosphatase appeared in mature chondrocytes just prior to mineralisa- 

 tion and was stronger in chondrocytes within the mineralising zone. The highest 

 levels of alkaline phosphatase were seen in osteoblasts and in periosteal cells of the 

 condylar process. These findings confirm for this tissue the well documented associ- 

 ation of alkaline phosphatase with cells involved in calcification (see Cabrini, 1961 

 for review). 



