The Comparison And Mechanism Of Pleurodesis Induced By Talc Or Silver Nitrate

Objective: To study the mechanisms of experimental pleurodesis in rats induced by silver nitrate or talc, and the role of TNF- a, ICAM-1 and NF- kB in the mechanisms of experimental pleurodesis in rats induced by silver nitrate or talc. To compare the pleurodesis results from the intrapleural injection of silver nitrate and talc slurry over an observation period of one month in rats.Methods: 66 Adult Sprague-Dawley rats underwent pleurodesis as follows: 6 rats received 1ml 0.9% Natrii Chloride solution; 30 rats received 1ml of 0.1% silver nitrate; and 30 rats received 200mg/kg of talc slurry in 1 ml intrapleurally. Six rats in each group were killed at day1, day4, day7, day 14 and day28 after intrapleural injection. The degree of gross pleurodesis, the amount of microscopic pleural fibrosis and inflammation were graded on a scale of 0 to 4. Pleural fluid at the first 24 hours, hisopathological alternation of experimental lung were observed. TNF-a in plasma and 24h pleural fluid were determined by ELISA. The NF-kB activation and ICAM-1 expression of the experimental lung tissues were examined by immunohistochemistry and image analysis. The accumulation of polymorphonuclear leukocytes in lung tissues was determined by the myeloperoxidase(MPO) assay.Results: The mean+SEM gross pleurodesis score in the rats that received silver nitrate was 3.3+0.2, which was significantly higher than the score of 1.8+0.1 in the rats that received talc. The mean gross pleurodesis score was significantly higher at each of the observation times(P<0.05), except at the first seven days, in the rats that received silver nitrate. The NF- kB activation and ICAM-1 expression were both positive staining in the cytoplasm for each observation times of two groups. They began to increase at the dayl and peak at the week2, and then decreased gradually to the contrast level at the week4. The ICAM-1 expression was positively correlated with the NF- k B activation in lung tissues. The MPO activation began to increase at the dayl and peak at the week2, and then decreased gradually to the contrast level at the week4, and was significantly higher (P<0.05) in the rats that received silver nitrate at each of the observation times. So does the microscopic pleural fibrosis and inflammation grades. The volume of pleural fluid at 24h following silver nitrate administration were significant higher thanthat of talc, while the TNF-a in plasma were on the contrary. The TNF-a in 24h plasma were significant lower in 24h pleural fluid at the same experimental group. Conclusion: The intrapleural injection of 1ml of 0.1% silver nitrate produces a better pleurodesis than does the intrapleural injection of 200mg/kg of talc slurry in rats. The up-regulation of NF- k B activation and ICAM-1 expression is important in the process of pleurodesis. TNF- a is important in the process of pleurodesis. The mechanisms responsible for the pleurodesis is that the inflammatory reaction to the administration of sclerosing agent. The efficacy of silver nitrate as a sclerosing agent in humans should be evaluated.