Role of constitutive cyclooxygenase-2 in prostaglandin-dependent secretion in mouse colon in vitro.
The relative contributions of cyclooxygenase (COX)-1 and COX-2 in mediating prostaglandin (PG)-dependent chloride secretion were investigated in segments of mouse colon mounted in Ussing-type diffusion chambers. COX-2 mRNA and protein were constitutively expressed as shown by reverse transcription-polymerase chain reaction and Western immunoblot, respectively. COX-2 immunoreactivity was detected immunohistochemically in cells lying subjacent to the crypt epithelial cells. In segments of colon mounted in Ussing chambers, arachidonic acid caused a concentration-dependent increase in short-circuit current that was blocked by piroxicam, the COX-2 inhibitor NS-398, and the COX-1 inhibitor SC-560. Exposure to the PG-dependent secretagogue, bradykinin, also caused an increase in short-circuit current that was not blocked by piroxicam or SC-560, and only by the highest dose of NS-398. When incubated in the presence of 10 microM arachidonic acid, segments of mouse colon produced both PGE(2) and PGD(2). Synthesis of PGE(2) but not PGD(2) was blocked by NS-398 and SC-560. These data demonstrate that both COX-1 and COX-2 are constitutively expressed in the mouse colon, and both contribute to PG-dependent electrolyte transport.
MacNaughton
W K
WK
Gastrointestinal Research Group and Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada. wmacnaug@ucalgary.ca
Cushing
K
K
D000818:Animals; D015153:Blotting, Western; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004573:Electrolytes / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D009578:Nitrobenzenes / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000378:metabolism*; D011453:Prostaglandins / Q000502:physiology*; D011720:Pyrazoles / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013449:Sulfonamides / Q000494:pharmacology
D002712:Chlorides; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D004573:Electrolytes; D007527:Isoenzymes; D008565:Membrane Proteins; D009578:Nitrobenzenes; D011453:Prostaglandins; D011720:Pyrazoles; C115461:SC 560; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases