Differences between duodenal and jejunal rat alkaline phosphatase

Objectives: The aim of this study was to kinetically characterize rat tissue-nonspecific-alkaline phosphatase (TNS-ALP) and intestinal (duodenal- and jejunal-IALP), and to determine the effect of substances known to affect phosphorylation/dephosphorylation on TNS- and IALP activity. Design and results: The ranking order of ALP activity (Kenzyme) was duodenal mucosa (IALP) > jejunal mucosa (IALP) > kidney (TNS-ALP) > brain (TNS-ALP). Levamisole was found to produce a concentration-dependent decrease of ALP activity in kidney and brain. However, levamisole had no effect on duodenal ALP activity and produced a concentration-dependent increase on jejunum ALP activity. In brain and jejunum homogenates, octreotide, a stable somatostatin analogue, produced a concentration-dependent increase in ALP activity. In relation to duodenum ALP activity, octreotide produced a biphasic effect. Reverse transcription-polymerase chain reaction showed the presence of IALP-I mRNA both in duodenal and jejunal mucosa, but IALP-II only in duodenal mucosa. Conclusions: The results show that duodenal- and jejunal-IALP differ in kinetic parameters and in drug sensitivity. Thus, we can speculate on a different physiologic role for duodenal- and jejunal-IALP, particularly in relation to their dephosphorylation targets.