PLATELETS AS A SOURCE OF SERUM ACID NITROPHENYLPHOSPHATASE*

Abstract
A significant proportion of serum enzyme activity against p-nitrophenyl-phosphate at acid pH originates from platelets and is liberated during clotting, particularly at 37[degree]C. Intact washed platelets in saline and unwashed platelets in platelet-rich plasma have activities up to 6.5 and 3 uM/109 platelets/hour respectively, and activity is greater after freezing. In patients with prostatic carcinoma, the abnormal enzyme is in the plasma.