HYDROPEROXIDE-INDUCED BRONCHOCONSTRICTION AND VASOCONSTRICTION IN THE ISOLATED RAT LUNG

The effects of different hydroperoxides on lung mechanics and perfusate flow rate and their mechanisms of action were studied in isolated perfused rat lungs. The administration of hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, linoleic acid hydroperoxide, and linoleic acid ethylester hydroperoxide (0.1-2 mM) to the perfusate caused a marked decreased in lung compliance, conductance, and perfusate flow rate, with constriction strength of t-butyl hydroperoxide > hydrogen peroxide > cumene hydro-peroxide > linoleic acid ethylester hydroperoxide > linoleic acid hydroperoxide. Although the hydroperoxides probably had to enter lung cells to exert their effects, no relationship was found between constriction strength and amount of hydroperoxide taken up by the lung. Reduced sensitivity was apparent after repeated dosing, depending on the length of time between dosing. The addition of the iron chelator Desferal (1 mM) had no effect on the hydroperoxide-induced broncho- and vasoconstriction, although free iron was reduced by 50% in the lungs. The administration of the antioxidants diphenyl-p-phenylenediamine (50-mu-M) or butylated hydroxyanisole (200-mu-M) to the perfusate 20 min prior to the hydroperoxide attenuated the hydroperoxide-induced effects as well as arachidonic acid-induced broncho- and vasoconstruction. Our findings have shown that hydroperoxides that can enter the lung cells will also induce both vaso- and bronchoconstriction in the isolated perfused rat lung.