Involvement of thromboxane in injury to isolated rat lungs perfused with phorbol myristate acetate in the presence and absence of neutrophils

Abstract

In a previous study, we demonstrated that a nontoxic concentration of phorbol myristate acetate (PMA) produced edema in isolated rat lungs which were coperfused with neutrophils (PMN). In this study, we examined whether prostaglandins or thromboxane were responsible for increases in pressure and/or edema in this preparation. In lungs perfused with PMA (14 ng/ml) and PMN (1 × 10 8), significantly greater amounts of thromboxane B 2 (TxB 2) and 6-keto-prostaglandin F 1α (6-keto-PGF 1α) were produced than in controls. Relative lung weights and increases in perfusion pressure correlated with concentrations of TxB 2 and 6-keto-PGF 1α that were produced. Indomethacin (10 μ m) or Dazmegrel (10 μ m) retarded the increase in perfusion pressure and prevented the increase in relative lung weight induced by PMA and PMN. When lungs were perfused with a high concentration of PMA (57 ng/ml) in the absence of added PMN, lungs also become edematous. Compared to controls, concentrations of TxB 2 and 6-keto-PGF 1α were elevated in media collected from this preparation. As with lungs perfused with PMN and PMA, increases in pressure and relative weights of lungs perfused with PMA (57 ng/ml) correlated with the concentrations of TxB 2 that were detected in perfusion media. Although indomethacin (10 μ m) and Dazmegrel (50 μ m) retarded the increase in perfusion pressure in this preparation, they only partially attenuated the increase in lung weight. These results suggest that, depending on the concentration, PMA can produce lung injury via different mechanisms. Thromboxane does not seem to be required for the genesis of edema induced by a high concentration of PMA in the absence of perfused neutrophils; however, it appears to play an obligatory role in the pathogenesis of edema induced by a low concentration of PMA in the presence of PMN.