1988 Volume 36 Issue 10 Pages 4182-4186
The activities of thiol proteinases and their endogenous inhibitors in musculus rectus femoriswere studied in control and exercised rats of various ages. Cathepsins B and H, both lysosomal thiolproteinases, showed different age-related changes in activity. Two forms of calcium-activatedneutral protease (CANP), μCANP and mCANP, differ from the lysosomal thiol proteinases withregard to age-related changes in activity. The activities of endogenous inhibitors of CANP, cathepsins B and H are apparently not affected by age. Among CANP, cathepsins B and H, only theactivity of CANP (the sum of μCANP and mCANP activities) in the 16-week-old rats was reducedafter training. Exercise had no effect on the activities of endogenous inhibitors in the 16-week-and98-week-old animals. The relative percentage of the activity of μCANP to the activities of μCANPplus mCANP did not change regardless of differences of age or exercise. These findings suggest thatfactors other than endogenous inhibitors may be involved in the age- and exercise-related changesin the activities of these thiol proteinases, and also that there is a close relationship between μCANP and mCANP in skeletal muscle.
