The actions of halothane, ibuprofen and BW755C on hypoxic pulmonary vasoconstriction

The effect of halothane on the pressor responses to hypoxia (3% O2, 5% CO2, balance N2) and to Angiotensin II (Ang II) (0.2 microgram) has been compared in an in vitro perfused and ventilated rat lung preparation in the presence and absence of agents known to block the lipoxygenase (BW755C) and/or the cyclooxygenase (ibuprofen) pathways for arachidonic acid metabolism. Preliminary studies established the stability of the preparation (experiment 1) during two hours of observation and allowed estimation of (experiment 2) the concentration of BW755C that inhibited the HPV response by 50% (ED50 = 125 microM). In experiment 3, the rat lungs were subdivided into four groups: A, B, C, and D. Group A received the drug solvent, and B received 17 microM ibuprofen. Groups C and D received ibuprofen and, in addition, an ED50 dose of BW755C. The lungs were then tested for their response to hypoxia. In addition, groups C and D were tested for their response to 0.2 microgram Ang II. 0.5 MAC halothane was introduced into the ventilatory circuit of A, B, and D. Group C received no halothane. Responses to hypoxia and Ang II (groups C and D) were measured. Halothane was terminated and a further hypoxic response was tested in groups A and B. The results show, in group A, that the addition of halothane reduced the response to hypoxia from (mean +/- SE cm H2O) 13.4 +/- 1.56 to 6.5 +/- 1.28, a 50% reduction. The addition of ibuprofen in group B caused a 33% increase in the response, and the addition of halothane now caused only a 30% decrease.(ABSTRACT TRUNCATED AT 250 WORDS)