Age-dependent changes in the activity of serum alkaline phosphatase in laboratory beagle dogs

In order to prepare background data for toxicity studies, serum alkaline phosphatase activity in a total of 5,242 male and female beagle dogs was surveyed for the sequence of changes in activity through aging. About 95% of the beagle dogs surveyed were 5 to 12 months of age, corresponding with the age usually employed in toxicity studies. Serum alkaline phosphatase (ALP) activity, about 460 IU/l at 5 months of age, steadily decreased and reached a level about one third of that (about 160 IU/l) at 12 months of age, and remained unchanged thereafter. The above findings were essentially the same irrespective of sex and breeding colony. The present results are useful information in the evaluation of blood chemistry data in toxicity studies.