A morphometric and functional study of the toxicity of atmospheric ammonia in the extrathoracic airways in pigs.

The effects of atmospheric ammonia (NH3) on the nasal and tracheal mucosa of pigs were investigated by morphometric and functional methods. Pigs were exposed to four concentrations of NH3 [5 (control), 25, 50 and 100 ppm] for 6 days in a specially designed air-pollutant exposure chamber. Samples were taken from the turbinates and the trachea, and the respiratory mucosa was examined by light and scanning electron microscopy. Dose-response curves to carbachol and isoproterenol were constructed using isolated strips of tracheal smooth muscle, with or without epithelium. In pigs exposed to ammonia, considerable mucosal injuries were observed in the turbinates but not in the trachea. The number of neutrophils in the epithelial layer and in the lamina propria, and epithelial hyperplasia were closely and significantly correlated with the concentrations of ammonia (r = 0.894, p < 0.001; r = 0.727, P < 0.001; and r = 0.818, p < 0.001, respectively). Except for the lamina propria, all these changes were significant (p < 0.05) at ammonia concentrations as low as 25 ppm. The percentage of the surface of the turbinate mucosa that was ciliated tended to decrease with increasing ammonia concentration (r = 0.439, p < 0.082). Ammonia induced smooth-muscle hyperresponsiveness to carbachol with a close linear correlation between individual values of the carbachol-induced maximal effect and the NH3 concentrations (r = 0.526, p < 0.003). While mechanical destruction of the epithelium induced an increase in Emax in the control group, no difference was observed between the intact and denuded strips from animals exposed to ammonia. The response to isoproterenol was not influenced by ammonia. It was concluded that quantitative histological analysis of the inflammatory infiltration and epithelial hyperplasia in the turbinates is a useful tool for quantifying the effects of atmospheric pollutants in pigs; a 6-day exposure to ammonia induces nasal irritation and functional disturbances of the tracheal smooth-muscle contractions at concentrations as low as 25 ppm.

Chronic exposure of pigs to airborne dust and endotoxins in an environmental chamber: technical note.

A new experimental setup was developed to expose pigs to dust and airborne endotoxins in an environmental chamber, at levels liable to be encountered in pig farm buildings. The following parameters were evaluated in a chamber containing two pigs of 10 kg body-weight: inhalable and respirable dust gravimetric concentrations were measured using area samplers and expressed as mg/m3. The respirable dust concentration was also measured using a "TM digital microP respirable dust-measuring instrument', which has been shown to give similar results to the gravimetric method. The endotoxin concentration was evaluated using the Limulus-assay and expressed as ng/m3 of air containing the inhalable or respirable dust or as ng/mg of inhalable and respirable dust. Feed flour dust was introduced into the chamber to obtain different concentrations of inhalable and respirable dust ranging from 3.62 to 76.66 mg/m3 and from 0.24 to 1.40 mg/m3, respectively. The endotoxin concentration was modulated by mixing the feed flour with Escherichia coli endotoxins before blowing it into the chamber. The endotoxin concentrations in the air containing inhalable or respirable dust ranged from 28.9 to 270.0 ng/m3 and from 2.22 to 36.38 ng/m3, respectively, depending on the amount of endotoxins added to the dust. Data were also obtained in a piggery. The experimental setup detailed in this paper could be used to study the significance of air contaminants in the development of pig respiratory diseases.

Quantitative assessment of aerial ammonia toxicity to the nasal mucosa by use of the nasal lavage method in pigs.

Effects of atmospheric ammonia (NH3) on the nasal mucosa and somatic growth were investigated in pigs exposed to 4 NH3 concentrations (0; 25; 50; and 100 ppm) for 6 days in a specifically designed air-pollutant exposure chamber. Nasal lavage (NAL) was applied to quantify the ammonia-induced inflammatory response by measuring the number of neutrophils and the albumin (porcine serum albumin) concentration in the NAL liquid. In control pigs, these variables remained unchanged throughout the exposure period. In all other groups, an important ammonia concentration-related increase was recorded. The equation of the linear regression line established between the mean values of the number of neutrophils (x 10(3)) per milliliter of NAL liquid (y) recorded at the end of the exposure period and the ammonia concentrations (ppm) was: y = 69.7 + 3.3 [NH3] (r = 0.979; P < 0.020). The increase in the neutrophil count was significant (P < 0.05) at concentrations as low as 25 ppm. For albumin concentration nanograms per milliliter, the corresponding equation was: y = 574 + 14.3 [NH3] (r = 0.953; P < 0.045). However, the first significant change (P < 0.05) in this variable was only obtained for the higher concentration (100 ppm). In exposed pigs, a concentration-related depression of somatic growth was observed. The equation of the regression line plotted relating the individual values of the changes in body weight gain recorded over the exposure period expressed as percentage of the initial body weight (y) and the ammonia concentration was: y = 3.507-0.203 [NH3] + 0.001 [NH3]2 (r = 0.55; P < 0.010).(ABSTRACT TRUNCATED AT 250 WORDS)

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 investigated 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 permeability and on the endotoxin-induced vascular response were also assessed using an isolated perfused lung preparation. The total pulmonary blood flow resistance (Rt) was partitioned into four components: arterial (Ra), pre-(Ra') and post-(Rv') capillary and venous (Rv). The capillary filtration coefficient (Kf,c) was evaluated by using a gravimetric technique. None of the concentrations of ammonia significantly 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 growth were observed. The equation of the regression line plotted relating the mean values of the changes in body weight gain recorded over the exposure period expressed as percentages of the initial body weight (y) and ammonia concentrations (x) was: y = 3.204 - 0.177x + 0.001x2 (r = 0.99; p < or = 0.013). Endotoxin infused in the perfusion liquid of lungs from unexposed animals for 180 min induced a significant 208% increase in Rt (p < 0.001) which can be ascribed to a 338 and 180% increase in Ra' and Rv', respectively. Endotoxin infusion also induced a 62% (p < or = 0.001) increase in the Kf,c. Exposure of pigs to ammonia at any concentration did not modify the baseline values of any hemodynamic or permeability parameters. However, the hemodynamic response to endotoxins in lungs from pigs exposed to 100 ppm was significantly altered. The increase in Rt, Ra', and Rv' observed in unexposed pigs was completely abolished as shown by the limited changes in Rt (+34.9%). An intermediate reaction (+131.7%) was obtained in pigs exposed to 50 ppm. This inhibiting effect of ammonia was closely correlated with gas concentration by a linear regression (r = 0.99; p < or = 0.037). The changes in the Kf,c recorded in the control group were not modified by exposure to ammonia. It was concluded that exposure of pigs to aerial ammonia 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.(ABSTRACT TRUNCATED AT 400 WORDS)

[Microclimate and air composition in a closed chamber meant for the study of the toxicity of atmospheric pollutants for the piglet]. / Microclimat et composition de l'air dans une enceinte fermée destinée à l'étude de la toxicité des polluants atmosphériques chez le porcelet.

An experimental model representing the pollution background in a pigpen was constructed in order to study the toxicology of pig respiratory air pollutants. Temperature, relative humidity, air-flow rate, total dust, total viable particles, endotoxins in respirable dust (< 5 microns) and ammonia were measured in a 1.9 m3 environmental chamber designed for piglets. The activity of 1 piglet was recorded on video. Temperature and relative humidity were respectively 23.9 +/- 1.3 degrees C and 70.5 +/- 8.3% (mean +/- SD). Air flow rate was 10 m3/h. Dust, viable particles, endotoxin and ammonia concentrations were respectively 7 +/- 2 particles/ml, 3.4 x 10(4) +/- 2.9 x 10(4) BCFP (bacterial colony-forming particles)/m3, 4.8 +/- 1.5 ng/m3 and 6 +/- 0.8 ppm (mean +/- SD). All these parameters were comparable to the lowest values recorded in pigpens.