High-molecular intestinal alkaline phosphatase by agarose gel electrophoresis

The presence of high-molecular intestinal ALP (HIALP) overlapping with bone ALP in the alpha(2)beta region has been demonstrated. In this study we evaluated a method of separating HIALP after its conversion into ALP(5) by the action of protease. Serum samples from patients were mixed with protease at a ratio of 5:1 and left at room temperature for more than 30 min. The protease-treated and nontreated samples were both subjected to agarose gel electrophoresis. Patients who showed a decrease in ALP(3) in the alpha2beta region and an increase in ALP(5) in the beta region were regarded as HIALP-positive. HIALP was observed in 26.7-33.1% of patients with liver diseases, collagen diseases, and diabetes mellitus. Renal disease was ABO blood group-dependent and showed high positive rates for blood groups B and O. The HIALP-positive rate was low (7.1-15.5%) in patients with cardiovascular diseases, malignant tumors, and other disorders. ALP(5) was also observed in 98.4% of HIALP-positive patients with liver diseases. In patients with collagen diseases or diabetes mellitus, the positive rate of ALP(5) was 40.4-66.7%. In conclusion, this method, in which HIALP is converted into ALP(5) by protease pretreatment and is separated from bone ALP, allows HIALP to be identified while other fractions remain unaffected.