Alteration of Cartilage Lysosomal Enzyme Activities during Development

Cartilage cathepsin D, cathepsin B and acid phosphatase activities decreased with maturation of Sprague-Dawley rats. Although this phenomenon may largely be due to an age-dependent decrease in cell concentration at young ages (1–8 weeks), in older (8–25 weeks) rats there appeared to be a decrease in enzyme activity per cell. The dimunition in cartilage cathepsin D activity coincided with an apparent decrease in its concentration. In addition, the inverse correlation between rat age and cartilage lysosomal enzyme activities was, at least in part, tissue specific as the pattern of liver lysosomal enzyme activities was quite different from that noted with cartilage. Interestingly, hypophysectomy greatly diminished age-related modulations in lysosomal enzyme activities suggesting that one or more pituitary hormones may be involved in the mechanism of this age-dependent phenomenon. In addition, cartilage growth rate appeared to be correlated with the level of cartilage lysosomal enzyme activities, indicating that these enzymes may be related to the biochemical mechanism of cartilage growth and development.