The effect of different buffers and amounts of intestinal alkaline phosphatase isoforms on total alkaline phosphatase activity

Abstract

Background: The transphosphorylating accepter buffers (2-amino-2-methyl-1-propanol, AMP; N-methyl- d-glucamine, MEG; diethanolamine, DEA and 2-ethylaminoethanol, EAE) have been widely used for the measurement of serum total alkaline phosphatase activity (ALP) in clinical laboratories, and the individual isozyme are activated differently by respective buffers. Materials and methods: We examined the activity of serum ALP using four buffers with levels of both high molecular weight intestinal alkaline phosphatase (HIAP) and normal molecular weight intestinal alkaline phosphatase (NIAP). We classified 80 healthy subjects into two groups of blood group B or O secretors ( n=36) and other blood groups ( n=44). Results: The mean ALP activities at fasting in blood group B or O secretors from AMP, MEG, DEA and EAE methods were 15.5%, 24.0%, 11.0% and 22.1% higher than those in other blood groups, respectively. The reference ranges of ALP activity at fasting with the AMP method in blood group B or O secretors and other blood groups were 63.5±17.4 U/l (mean±S.D.) and 55.0±14.5 U/l (mean±S.D.), respectively. The difference between the reference ranges of ALP activity in blood group B or O secretors and other blood groups was statistically significant ( p<0.01). HIAP and NIAP in serum at fasting only appeared in blood group B or O secretors, and the activities of HIAP and NIAP were 4.7±3.4 U/l (mean±S.D.) and 2.2±1.2 U/l (mean±S.D.), respectively. The activity of ALP−(HIAP+NIAP) in blood group B or O secretors was 56.6±15.1 U/l (mean±S.D.), and this reference range was approximately the same as the ALP activity (55.0±14.5 U/l) of other blood groups. The same results were observed with MEG, DEA and EAE methods. Conclusions: These results suggested that the differences in ALP activity in blood group B or O secretors and other blood groups were closely related to the HIAP and NIAP levels.