Rat lung phospholipid fatty acid composition in prepregnant, pregnant, and lactating rats: relationship to ozone-induced pulmonary toxicity.

Our laboratory has demonstrated recently that pulmonary inflammation induced by acute ozone exposure is much more severe in late stage pregnant and lactating rats than in postlactating rats or age-matched virgin females. It is currently widely believed that such pulmonary damage results, at least in part, from the reaction of ozone at sites of unsaturation in phospholipid fatty acid (PLFA) molecules located in the epithelial fluid layer lining the lung surfaces and/or the plasma membranes of epithelial cells underlying this fluid layer. The objective of this study was to compare the PLFA composition of lung tissue and surfactant from ozone-sensitive late stage pregnant and lactating rats with comparable tissue from relatively ozone-insensitive age-matched prepregnant (virgin female) rats to explore the possibility that changes in lung PLFA composition during pregnancy and/or lactation contribute to the enhanced sensitivity of these physiologic states to ozone. In addition, the correlation of changes in plasma PLFA composition with those in lung was investigated. There were minor differences in the composition of lung tissue and surfactant PLFAs between prepregnant rats and pregnant rats at day 17 of gestation and only slightly greater differences between prepregnant and lactating rats. Changes from the prepregnant state in the PLFA composition of lung tissue, but not surfactant, correlated with changes in the plasma only in lactating rats and not in pregnant rats. Overall, the double bond index of PLFAs in surfactant and lung tissue was decreased in pregnant and lactating rats compared with prepregnant rats. Thus, the increased sensitivity of pregnant and lactating rats to ozone-induced lung injury cannot be attributed to an increased availability of unsaturated fatty acids. In addition, the arachidonic acid composition of phospholipids did not appear to explain differences between prepregnant rats and pregnant or lactating rats in their inflammatory response to ozone. In conclusion, there is no evidence that the relatively minor changes in lung tissue PLFA composition which occur during pregnancy and lactation predispose rats in these physiologic states to ozone-induced pulmonary toxicity.