Effects of Some Autacoids on Breathing and Perfusion Flow in the Isolated Perfused Rat Lung

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Abstract
The effects of three autacoids ((5‐hydroxytryptamine (5‐HT), bradykinin and acetylcholine (Ach)) on breathing and pulmonary circulation were studied in the isolated perfused and ventilated rat lung after intravascular injection or intrabronchial instillation. 5‐HT, bradykinin and Ach all caused a dose related reduction in breathing, after injection into the pulmonary artery, with Ach being the most potent. With regard to effects on the pulmonary circulation, a dose‐related reduction in perfusate flow was noted with bradykinin and 5‐HT with bradykinin being about 10 times more potent than 5‐HT. Ach did not reduce or increase perfusate flow. After intrabronchial instillation only 5‐HT caused reduced perfusate flow. Effects on breathing were difficult to evaluate with this route of administration. The isolated perfused and ventilated lung seems to be a usable model to simultaneously study effects on respiration and pulmonary circulation.