EFFECT OF AGE ON THE LEVEL OF SERUM ALKALINE PHOSPHATASE ACTIVITY OF JAPANESE BLACK STEERS

The level of serum alkaline phosphatase activity was determined in 7 Japanese Black steers at different ages. The isoenzyme activity of non-bone origin was estimated using a heat-inactivation technique. The activity of serum alkaline phosphatase (SALP, K-A unit) decreased as age (AGE, mo.) increased: SALP = 14.15 - 0.17 (${\pm}\;0.03$) AGE, r = -0.81, P<0.01, $S.E.\;{\pm}\;0.28$. The variation of the activity was greater in younger age than the older. The temperature of $58^{\circ}C$ for the treatment of heat inactivation of bovine serum appeared to be suitable. The percentage of heat inactivated enzyme activity negatively correlated with age and positively with the level of serum alkaline phosphatase activity. The activity of SALP of non-bone origin was inferred to stay at about constant level irrespective of age and that of bone origin decreased with age.