Abstract
Summary
The effect of 50 mg of phenoxybenzamine on the pulmonary and systemic circulations were studied in unanesthetized normal calves and calves with Brisket Disease. Typically, within 10 seconds of injection the PA pressure increased significantly reaching a peak in 30-60 sec. There was a transient fall in Ao pressure and rise in heart rate, while CO and PAW pressure remained constant. Phentolamine failed to induce similar effects in calves. Pretreatment of calves with indomethacin significantly blunted the phenoxybenzamine induced PA pressure response. Thus, this study demostrates that the bovine pulmonary circulation is sensitive to relatively small amounts of phenoxybenzamine. The mechanism of this effect is unknown.
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