Abstract
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 μM arachidonic acid, segments of mouse colon produced both PGE2 and PGD2. Synthesis of PGE2but not PGD2 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.
Footnotes
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Send reprint requests to: Wallace MacNaughton, Ph.D., Department of Physiology and Biophysics, University of Calgary, 3330 Hospital Dr. NW, Calgary, Alberta, Canada T2N 4N1. E-mail:wmacnaug{at}ucalgary.ca
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↵1 This study was supported by a New Investigator Establishment grant from the Canadian Association of Gastroenterology and the Medical Research Council of Canada.
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↵2 W.K.M. is an Alberta Heritage Foundation for Medical Research Scholar.
- Abbreviations:
- PG
- prostaglandin
- COX
- cyclooxygenase
- RT-PCR
- reverse transcription-polymerase chain reaction
- Isc
- short-circuit current
- IR
- immunoreactivity
- Received August 2, 1999.
- Accepted January 12, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
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