Acute Effects of Endotoxin Inhalation on the Respiratory Tract in Pigs: Interaction with Ammonia

Abstract

The acute respiratory effects of endotoxin inhalation (0–400 μ/kg) have been evaluated in pigs. Endotoxin (LPS from Escherichia coli 0127:B8 and 055:B5) nebulization had no direct effect on the nasal mucosa. An in vitro bronchial hyperreactivity to acetylcholine and histamine, related to the endotoxin dosage, was recorded. In the lung, significant endotoxin dose-dependent increases in the total cell, alveolar macrophage, and neutrophil counts in the BAL fluid were recorded. Following intrabronchial administration of endotoxin, the cellular response was significantly higher than that obtained after nebulization. Neither the dry to wet lung weight ratio (DW/WW) nor the albumin concentration in the BAL fluid was affected. When endotoxins were infused intravenously, the lung cellular response was accompanied by an increase in the albumin concentration in the BAL fluid. In pigs exposed for 6 days to 50 ppm ammonia, endotoxin nebulization induced a significant increase in the albumin concentration and tented to increase the number of neutrophils in the NAL fluid. Ammonia did not alter the lung response to endotoxin inhalation. It was concluded that endotoxin nebulization can produce bronchial hyperreactivity and a cellular inflammatory response in the lung, but without inducing pulmonary edema. Ammonia can interfere with nasal response to endotoxins. The weak response to endotoxin inhalation could be ascribed to the barrier role played by the alveolar epithelium and to dilution of the aerosol throughout the respiratory system.