Differences between duodenal and jejunal rat alkaline phosphatase.
OBJECTIVE
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.


RESULTS
The ranking order of ALP activity (K(enzyme)) 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.
Calhau
C
C
Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal. ccalhau@med.up.pt
Martel
F
F
Hipólito-Reis
C
C
Azevedo
I
I
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology; D007583:Jejunum / Q000187:drug effects / Q000201:enzymology*; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D007978:Levamisole / Q000494:pharmacology; D008297:Male; D009596:Nitrophenols / Q000378:metabolism; D015282:Octreotide / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D000276:Adjuvants, Immunologic; D004791:Enzyme Inhibitors; D006728:Hormones; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D012333:RNA, Messenger; D007978:Levamisole; C008644:nitrophenylphosphate; D000469:Alkaline Phosphatase; D015282:Octreotide