BACKGROUND: Some of the prominent features of silicosis are hyperplasia and hypertrophy of epithelial type II cells, which in experimental animals are often accompanied by accumulation of phospholipids in the lung. METHODS: The total phospholipid content of lung lavage fluid and its composition in 28 granite stone cutters with long term exposure to silica dust (23 with radiological silicosis) was compared with that of lavage fluid in 15 normal volunteers, 15 patients with untreated idiopathic pulmonary fibrosis, and 19 patients with untreated stage 2 or 3 sarcoidosis. All lavage fluid was obtained at the time of first pulmonary investigation, which also included lung function tests. RESULTS: In the normal subjects total phospholipid content was 1.13 (0.16) micrograms phosphorus/ml of lung lavage, in the patients with idiopathic pulmonary fibrosis 0.52 (0.07) microgram/ml (p < 0.05), and in the patients with sarcoidosis 1.02 (0.20) microgram/ml composition being in the range reported in humans. In the patients with silicosis total phospholipid content was significantly decreased to an average of 0.46 (0.08) microgram/ml compared with the findings in normal subjects and patients with sarcoidosis. Within the group exposed to silica changes in total phospholipid content did not correlate with the severity of the radiographic disease, changes in lung function, the cellularity of lung lavage fluid, or hyaluronate concentrations. The secretory capacity of rat epithelial type II cells was not significantly different when cultured with bronchoalveolar lavage fluid from all four groups of subjects. CONCLUSIONS: Total phospholipid content in lung lavage fluid was significantly reduced in granite workers with radiological evidence of lung disease, but showed no correlation with radiological or functional markers of disease severity.
BACKGROUND: Some of the prominent features of silicosis are hyperplasia and hypertrophy of epithelial type II cells, which in experimental animals are often accompanied by accumulation of phospholipids in the lung. METHODS: The total phospholipid content of lung lavage fluid and its composition in 28 granite stone cutters with long term exposure to silica dust (23 with radiological silicosis) was compared with that of lavage fluid in 15 normal volunteers, 15 patients with untreated idiopathic pulmonary fibrosis, and 19 patients with untreated stage 2 or 3 sarcoidosis. All lavage fluid was obtained at the time of first pulmonary investigation, which also included lung function tests. RESULTS: In the normal subjects total phospholipid content was 1.13 (0.16) micrograms phosphorus/ml of lung lavage, in the patients with idiopathic pulmonary fibrosis 0.52 (0.07) microgram/ml (p < 0.05), and in the patients with sarcoidosis 1.02 (0.20) microgram/ml composition being in the range reported in humans. In the patients with silicosis total phospholipid content was significantly decreased to an average of 0.46 (0.08) microgram/ml compared with the findings in normal subjects and patients with sarcoidosis. Within the group exposed to silica changes in total phospholipid content did not correlate with the severity of the radiographic disease, changes in lung function, the cellularity of lung lavage fluid, or hyaluronate concentrations. The secretory capacity of rat epithelial type II cells was not significantly different when cultured with bronchoalveolar lavage fluid from all four groups of subjects. CONCLUSIONS: Total phospholipid content in lung lavage fluid was significantly reduced in granite workers with radiological evidence of lung disease, but showed no correlation with radiological or functional markers of disease severity.