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The production of reduced forms of O2 in oxidant injury can lead to lipid peroxidation, which would pose a threat to cell membrane integrity and therefore to signal transduction pathways located in the membrane. We studied the effects of oxidant injury with t-butyl hydroperoxide (tBOOH) on signal transduction in rat type II pneumocytes in culture. Exposure of 1 x 10(6) type II pneumocytes to tBOOH concentrations less than or equal to 100 microM did not cause significant release of lactate dehydrogenase and was therefore termed sublethal. Exposure to sublethal concentrations of tBOOH caused a dose-dependent inhibition of surfactant secretion stimulated both by terbutaline (10(-4)M) and by extracellular ATP (10(-5)M). Adenosine 3',5'-cyclic monophosphate production in response both to terbutaline and to extracellular ATP was also inhibited by exposure to 100 microM tBOOH. In addition, exposure to 100 microM tBOOH inhibited inositol phosphate formation in response to extracellular ATP. We conclude that sublethal oxidant injury inhibits not only receptor-mediated agonist stimulation of surfactant secretion but also receptor-mediated agonist stimulation of second messenger formation in type II pneumocytes in culture. Such inhibition may be important in the pathogenesis of both the adult and neonatal forms of respiratory distress syndrome, in which alveolar surfactant deficiency may be exacerbated by oxidant injury.

We studied the interactions of corticosteroids, thyroid hormones, and beta-agonist on surfactant phospholipids, pulmonary mechanics, and beta-receptor binding in fetal lambs. We infused cortisol (450 micrograms/h for 48 h), thyrotropin-releasing hormone (TRH) (25 micrograms/h for 48 h), and ritodrine (1.3 micrograms/kg/min for 24 h) independently, and in double (cortisol plus beta-agonist, cortisol plus TRH), and in triple (cortisol plus TRH plus beta-agonist) combinations into chronically catheterized fetal lambs between 0.88 and 0.90 gestation. Infusion of the triple combination of cortisol plus TRH plus beta-agonist resulted in a 20.9-fold increase in the saturated phosphatidylcholine content of fetal lung lavage, in a 5.8-fold increase in the saturated phosphatidylcholine content of whole fetal lung, and in a 13.3-fold increase in the saturated phosphatidylcholine content of fetal tracheal fluid. In addition, lung stability to inflation increased 3-fold, and lung stability to deflation increased 8-fold. The increases in the saturated phosphatidylcholine content of fetal lung lavage and tracheal fluid were greater than the effects of each hormone acting independently, or in the double combinations. The beta-receptor maximal binding capacity was increased 30% by the combined infusion of cortisol and TRH. In addition, the maximal binding capacity after cortisol plus TRH plus beta-agonist infusion was 54% greater than the maximal binding capacity after beta-agonist infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

We developed a colorimetric assay for determining metabolic activity (viability) of cells exposed to toxic agents. This system is based on the ability of mitochondrial enzymes in viable cells to modify a tetrazolium salt into a blue formazan product that can be detected spectrophotometrically at 570 nm. The assay works equally well for mammalian and insect cell lines and at 48 hr color formation is linear over a cell input range of 1.56-50 X 10(4) cells/ml. The inhibitory effects of T-2 mycotoxin on tetrazolium cleavage in L929 cells is comparable to that observed for protein and DNA synthesis (50% inhibition = 6-8 ng/ml). Using this system to analyze the lethal effect of T-2 toxin on cells from various animal species, it was found that bovine cells were the most sensitive (50% inhibition at 2.2 ng/ml) while hamster cells were the most resistant (50% inhibition at 26.2 ng/ml). Murine cells exhibited intermediate sensitivity (50% inhibition at 10.9 ng/ml). Variable toxin susceptibility was also observed among different cell types. Lymphocytes were 3-fold more sensitive to the T-2 inhibitory effects than comparable tissue culture cell lines. These data indicate that the colorimetric assay system could have broad applications in toxicological studies. Further, the observed differences in species sensitivity may provide insight into the primary mechanism of the T-2 toxin-cell interaction that ultimately leads to cell death.