Radioimmunoassay of human intestinal alkaline phosphatase

Abstract

A new method of radioimmunoassay using duoble antibody method for human intestinal alkaline phosphatase (ALP) was first elabolated.
The following results were obtained:
1) In this system, optimal antibody concentration is 10, 000 times dilution of original anti-serum and optimal assay range is 0.5 to 25ng. Enzymatic activity of 1ng intestinal ALP is 4.1 King-Armstrong units.
2) In this system, the sera including intestinal ALP are divided to two groups. One group shows dose response curve similar to those of purified intestinal ALP and the other shows lesser. This reason is not clear. Hepatic ALP, osseous ALP and placental ALP in the sera show no response in this system.
3) In this system, B/T value of 50μg of purified human placental ALP is almost equal to 1ng of purified human intestinal ALP. B/T value of 50μg of purified human intestinal ALP is almost equal to 5ng of purified human placental ALP similarly. This shows cross-reaction exists between intestinal and placental ALPs at high concentration.