We have previously shown that
phosgene markedly increases lung
weight gain and pulmonary vascular permeability in rabbits. The current experiments were designed to determine whether
cyclooxygenase- and
lipoxygenase-derived mediators contribute to the
phosgene induced
lung injury. We exposed rabbits to
phosgene (1,500 ppm/min), killed the animals 30 min later, and then perfused the lungs with a saline
buffer for 90 min.
Phosgene markedly increased lung
weight gain, did not appear to increase the synthesis of
cyclooxygenase metabolites, but increased 10-fold the synthesis of
lipoxygenase products. Pre- or posttreatment with
indomethacin decreased
thromboxane and
prostacyclin levels without affecting
leukotriene synthesis and partially reduced the lung
weight gain caused by
phosgene.
Methylprednisolone pretreatment completely blocked the increase in
leukotriene synthesis and lung
weight gain. Posttreatment with
5,8,11,14-eicosatetraynoic acid (
ETYA), a nonmetabolized competitive inhibitor of
arachidonic acid metabolism, or the
leukotriene receptor blockers,
FPL 55712 and
LY 171883, also dramatically reduced the lung
weight gain caused by
phosgene. These results suggest that
lipoxygenase products contribute to the
phosgene-induced lung damage. Because
phosgene exposure did not increase
cyclooxygenase synthesis or pulmonary arterial pressure, we tested whether
phosgene affects the lung's ability to generate or to react to
thromboxane. Infusing
arachidonic acid increased
thromboxane synthesis to the same extent in
phosgene-exposed lungs as in control lungs; however,
phosgene exposure significantly reduced pulmonary vascular reactivity to
thromboxane but not to angiotension II and KCl.