CHANGES IN INTESTINAL ALKALINE-PHOSPHATASE ISOFORMS IN HEALTHY-SUBJECTS BEARING THE BLOOD-GROUP SECRETOR AND NON-SECRETOR

We found the high molecular mass intestinal alkaline phosphatase (HIAP ) and normal molecular mass intestinal alkaline phosphatase (NIAP) in serum at fasting and after fatty meal by use of 6.0% polyacrylamide ge l electrophoresis (PAGE) in the presence of 1% Triton X-100. HIAP only appeared in serum of Lewis blood group secretors {Le(a - b +)}, and H IAP levels were dependent on ABO blood groups. Among the secretors, th e highest activities of HIAP in fasting serum were observed in subject s with blood groups O and B (8.6 +/- 1.4 U/1; mean +/- SD) and the low est activities were associated with blood group A (0.7 +/- 0.2 U/1; me an +/- SD), and the HIAP activities did not change after fatty meal. I n contrast, NIAP was present in the serum of both secretors and non-se cretors regardless of ABO blood group. Trace amounts of NIAP remained in fasting serum; however serum NIAP activities rose sharply after fat ty meal. The remaining ratios of NIAP activity at fasting and 9 h afte r fatty meal of secretors were approximately the same as those of nons ecretors. The electrophoretic mobility on PAGE or the apparent molecul ar mass estimated by gel filtration of serum NIAP in secretors was sli ghtly different from that in non-secretors. In addition, HIAP can be n ormalized to NIAP on PAGE in the absence of Triton X-100, and the elec trophoretic mobility of normalized-NIAP was identical to that of origi nal NIAP in secretors. Accordingly, it can be concluded that the struc ture of serum NIAP in the secretor was different from that in the non- secretor, because HIAP is only formed by serum NIAP in the secretor. T hese results suggest that differences in serum NIAP in the secretor an d the non-secretor may be closely related to the appearance of IAP in the circulation. (C) 1998 Elsevier Science B.V. All rights reserved.