Characterization of cytochrome P-450-dependent arachidonic acid metabolism in rabbit intestine.
We characterized cytochrome P-450-dependent arachidonate (P-450-AA) metabolism throughout the intestinal tract, since some metabolites derived via this pathway modify epithelial ion transport and regional blood flow. Microsomes (0.3 mg/ml) were prepared from each region of the intestines of anesthetized New Zealand White male rabbits and incubated with [14C]AA (7 microM) for 30 min at 37 degrees C. In the presence of NADPH (1 mM), ileal microsomes exhibited the greatest P-450-AA metabolism, whereas duodenal microsomes exhibited little or no activity. For jejunal, ileal, and cecal microsomes, AA metabolism was reduced in the absence of NADPH and by boiling microsomes, was unaffected by indomethacin (10 microM) and BW-755C (50 microM), but was significantly attenuated by the P-450 enzyme inhibitors, 7-ethoxyresorufin (1 microM) and SKF-525A (100 microM). However, colonic (ascending, transverse, and descending) microsomal activity was inhibited by both P-450 and lipoxygenase inhibitors. Analysis of ileal AA metabolites by high-pressure liquid chromatography and negative ion chemical ionization gas chromatography-mass spectrometry revealed products corresponding to monohydroxyeicosatetraenoic acids (HETEs). Semiquantitative analysis showed that 20-, 19-, 18-, 17-, and 16-HETEs were present in a ratio of 6.2:3.3:0.3:0.1:0.1, respectively. Furthermore, ileal P-450-HETEs dilated the isolated perfused mesenteric bed, as did 20-HETE, the predominant ileal AA metabolite. Because 20-HETE was also shown to affect epithelial ion transport, we suggest that P-450-AA metabolites may make important contributions to intestinal function.
Macica
C
C
Department of Pharmacology, New York Medical College, Valhalla 10595.
Balazy
M
M
Falck
J R
JR
Mioskowski
C
C
Carroll
M A
MA
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002853:Chromatography, Liquid; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D007082:Ileum / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D011817:Rabbits; D014018:Tissue Distribution
D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System