Phenylbutazone increases right atrial pressure and heart rate of
running horses.
Mitten, L. A., K. W. Hinchcliff, and J. L. Pate.
Exercise Physiology Program, Department of Veterinary Clinical
Sciences, College of Veterinary Medicine, and Department of Dairy
Science, College of Agriculture (Pate), The Ohio State University,
Columbus, OH 43210-1089
APStracts 3:0127A, 1996.
The effect of inhibition of cyclooxygenase activity on the hemodynamic
response to exertion was examined in 6 horses. Rates of oxygen
consumption and carbon dioxide production, and carotid, pulmonary
artery and right atrial pressures were measured while the horses
performed a standardized exercise test on a treadmill after treatment
with phenylbutazone or a placebo. Phenylbutazone (8.8 mg(kg-1 PO for
2 days and 4.4 mg(kg-1 i.v. 60 min before exertion) abolished the
exertion-induced increases in plasma 6-keto-PGF1a and thromboxane B2
concentrations, confirming inhibition of cyclooxygenase activity.
Phenylbutazone treatment resulted in significantly (p < 0.05)
higher heart rates and right atrial pressures during exertion than
did treatment with placebo, which may have been due to increased
myocardial sensitivity to sympathetic stimulation and/or decreased
venous compliance. There was not a detectable effect of
phenylbutazone on carotid or pulmonary artery pressures, oxygen
consumption, carbon dioxide production or blood lactate
concentration. Changes in plasma volume during exertion were not
influenced by phenylbutazone. These results demonstrate that
cyclooxygenase products likely mediate or modulate some of the
systemic hemodynamic responses to exertion in horses.
Received 5 January 1995; accepted in final form 9 February 1996.
APS Manuscript Number A12-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96