Chicken Serum Alkaline Phosphatase

A kinetic method for the determination of alkaline phosphatase (AP) was applied to chicken serum. A buffer system of 2,2′dihydroxy-diethylamine (DEA) was found to give 3 to 5 times the activity of glycine, barbital, or carbonate buffers. The conditions for AP assay were: 1.0 M DEA-HCl, pH 9.9, 15 mM. p-nitrophenyl phosphate, and 5 mM. Mg++ at a temperature of 25° C. The initial rate of enzyme activity was followed at 405 nm. for 1 to 3 min. in a recording spectrophotometer. Thirty μl. of serum were sufficient for assay. The kinetic method allows assay of samples with a wide range of AP activity. Adult males had AP values of 336 ± 43 mU./ml. of serum. Laying hens consuming a diet adequate in calcium had 626 ± 104 mU./ml. of serum. When the diet was deficient in calcium the serum AP activity of laying hens increased to 5,517 ± 1,107 mU./ml. l-homoarginine (Harg) inhibited serum AP activity to a greater extent than an equimolar concentration of l-phenylalanine (Phe). The serum AP activity of cocks was more sensitive to both Harg and Phe than that of laying hens. In mammals Phe is a specific inhibitor of intestinal AP and Harg an inhibitor of bone and liver AP. Although serum AP activity of laying hens was increased 8 fold by a dietary calcium deficiency, there was not a differential response to inhibition by Harg and Phe.