EFFECTS OF ATMOSPHERIC AMMONIA ON PULMONARY HEMODYNAMICS AND VASCULAR-PERMEABILITY IN PIGS - INTERACTION WITH ENDOTOXINS

The influence of atmospheric ammonia on the somatic growth, the plasma cortisol and ammonia concentrations, and cell blood counts was invest igated in pigs exposed to four concentrations (0, 25, 50, and 100 ppm) for 6 days in a specifically designed air-pollutants exposure chamber . The effects of this gas on pulmonary vascular hemodynamics and perme ability and on the endotoxin-induced vascular response were also asses sed using an isolated perfused lung preparation. The total pulmonary b lood flow resistance (R(t)) was partitioned into four components: arte rial (R(a)), pre-(R(a')) and post-(R(v')) capillary and venous (R(v)). The capillary filtration coefficient (K-f,K-c) was evaluated by using a gravimetric technique. None of the concentrations of ammonia signif icantly modified the plasma cortisol and ammonia concentrations or the differential leukocyte percentages and total white blood cell count, suggesting an absence of stress related to ammonia. In exposed animals , lethargy and a concentration-related depression of the somatic growt h were observed. The equation of the regression line plotted relating the mean values of the changes in body weight gain recorded over the e xposure period expressed as percentages of the initial body weight (y) and ammonia concentrations (x) was: y = 3.204 - 0.177x + 0.001x(2)(r = 0.99; p less than or equal to 0.013). Endotoxin infused in the perfu sion liquid of lungs from unexposed animals for 180 min induced a sign ificant 208% increase in R(t) (p < 0.001) which can be ascribed to a 3 38 and 180% increase in R(a') and R(v'), respectively. Endotoxin infus ion also induced a 62% (p less than or equal to 0.001) increase in the K-f,K-c. Exposure of pigs to ammonia at any concentration did not mod ify the baseline values of any hemodynamic or permeability parameters. However, the hemodynamic response to endotoxins in lungs from pigs ex posed to 100 ppm was significantly altered. The increase in R(t), R(a' ), and R(v') observed in unexposed pigs was completely abolished as sh own by the limited changes in R(t) (+34.9%). An intermediate reaction (+131.7%) was obtained in pigs exposed to 50 ppm. This inhibiting effe ct of ammonia was closely correlated with gas concentration by a linea r regression (r = 0.99; p less than or equal to 0.037). The changes in the K-f,K-c recorded in the control group were not modified by exposu re to ammonia. It was concluded that exposure of pigs to aerial ammoni a concentrations from 0 to 100 ppm for 6 days has no direct effect on the pulmonary microvascular hemodynamics and permeability and induces no stress response. A marked depressive effect on the somatic growth i s observed at concentrations greater than 25 ppm. Concentrations great er than 50 ppm can modulate the pulmonary vascular response to endotox ins. (C) 1994 Academic Press, Inc.