Objective—To assess gene expressions of cyclooxygenase-1 and -2 in oral, glandular gastric, and urinary bladder mucosae and determine the effect of oral administration of phenylbutazone on those gene expressions in horses.
Animals—12 healthy horses.
Procedures—Horses were allocated to receive phenylbutazone or placebo (6 horses/group); 1 placebo-treated horse with a cystic calculus was subsequently removed from the study, and those data were not analyzed. In each horse, the stomach and urinary bladder were evaluated for ulceration via endoscopy before and after experimental treatment. Oral, glandular gastric, and urinary bladder mucosa biopsy specimens were collected by use of a skin punch biopsy instrument (oral) or transendoscopically (stomach and bladder) before and after administration of phenylbutazone (4.4 mg/kg, PO, q 12 h) in corn syrup or placebo (corn syrup alone) for 7 days. Cyclooxygenase-1 and -2 gene expressions were determined (via quantitative PCR techniques) in specimens collected before and after the 7-day treatment period and compared within and between groups. Prior to commencement of treatment, biopsy specimens from 7 horses were used to compare gene expressions among tissues.
Results—The cyclooxygenase-1 gene was expressed in all tissues collected. The cyclooxygenase-2 gene was expressed in the glandular gastric and bladder mucosae but not in the oral mucosa. Cyclooxygenase gene expressions were unaffected by phenylbutazone administration.
Conclusions and Clinical Relevance—Cyclooxygenase-2 was constitutively expressed in glandular gastric and bladder mucosae but not in the oral mucosa of healthy horses. Oral administration of phenylbutazone at the maximum recommended dosage daily for 7 days did not affect cyclooxygenase-1 or -2 gene expression.
Objective—To determine expression of cyclooxygenase (COX) genes 1 and 2 (also called prostaglandin-endoperoxide synthases 1 and 2) and stability of housekeeping gene expression during low-flow ischemia and reperfusion in the jejunum of horses.
Animals—5 healthy adult horses.
Procedures—Horses were anesthetized, and two 30-cm segments of jejunum were surgically exteriorized. Blood flow was maintained at baseline (untreated) values in 1 (control) segment and was decreased to 20% of baseline (low-flow ischemia) for 75 minutes, followed by 75 minutes of reperfusion, in the other (experimental) segment. Biopsy samples were collected from experimental segments at baseline (T0), after 75 minutes of ischemia (T1), and after 75 minutes of reperfusion (T2); samples were collected from control segments at T0 and T2. Horses were euthanized 24 hours after induction of ischemia (T3), and additional samples were collected. Samples were evaluated histologically. Total RNA was extracted; expression of COX genes and stability of 8 housekeeping genes were determined via quantitative real-time PCR assays.
Results—COX-1 and COX-2 genes were constitutively expressed in baseline samples. Low-flow ischemia resulted in significant upregulation of COX-2 gene expression at each subsequent time point, compared with baseline values. The most stably expressed reference genes were β-actin and hypoxanthine phosphoribosyltransferase, whereas glyceraldehyde 3-phosphate dehydrogenase and β-2 microglobulin were the least stably expressed.
Conclusions and Clinical Relevance—Low-flow ischemia resulted in upregulation of COX-2 gene expression in the jejunum of horses. Housekeeping genes traditionally used as internal standards may not be stable in this tissue during arterial low-flow ischemia and reperfusion.