Abstract

A very rapid method of agar gel electrophoresis on glass slides, together with a superior visualization technique employing simultaneous coupling of a hydrolysed naphthol substrate, have been developed for the identification of the tissues of origin of serum alkaline phosphatase. Combined with L-phenylalanine inhibition, specific for the intestinal enzyme, and heat inactivation, specific for the placental enzyme, the heterogeneity of serum alkaline phosphatase has been demonstrated. Normal adult serum contains predominantly liver-type alkaline phosphatase with a small but variable quantity of intestinal enzyme, and little or no bone enzyme.

In childhood and in infancy there is in addition a bone isoenzyme present, the amount gradually falling to adult levels with age. In pregnancy, the rise in serum alkaline phosphatase is due to the placental enzyme.

A study of nearly 2,000 sera has been undertaken and it is found that the bone enzyme is increased in osteoblastic bone diseases while in hepato-biliary disorders there is an increase in liver type enzyme. The main theories explaining the rise in serum alkaline phosphatase are examined.