Study The Relationship Between Serum Levels Of Silicon And Collagens In Rats Exposed To Silica At Different Stages

Objective: Silicosis which is the most common form of pneumoconiosis is statutory occupational diseases in China. Up to 2008, Reported cumulative total of 704,602 cases of occupational diseases, which accumulated up to 638,234 reported cases of pneumoconiosis cases. Among them, 10,829 new cases of pneumoconiosis cases,613 cases died and 811 cases of budding of cases. Almost 89.32% of pneumoconiosis was silicosis and CWP cases. The prevention condition becomes more and more serious. These data indicated that silicosis was one of the most dangerous occupational diseases. Though in some condition, silica exposure was stopped, silicosis still develops. With high concentration silica dust exposing, more and more younger cases were reported with more serious disease condition and higher mortality rate. Silicosis prevalence increased year by year, resulting in huge direct and indirect economic losses and heavy social burdens. At present, there is no effective early detection (screening) and effective health care approach to silicosis and exposure. Once diagnosed with conventional chest X-ray, pulmonary fibrosis can be reversed with no drugs. Therefore, seeking out biomarkers for the early diagnosis of silicosis and evaluation of pulmonary fibrosis has become a pressing issue in the study of silicosis. In resent years, many domestic and foreign scholars are making an effort to looking for biomarkers for early diagnosis (screening) of silicosis, however these are still at the laboratory stage and the effectiveness and feasibility of predicting silicosis and screening susceptible will take some time to verification. In our study we measure the serum levels of silicon with indirect atomic absorption spectrometric detection and compared with collagenⅠ,Ⅲto explore its meaning and values in the early diagnosis of silicosis.Methods:1. A total of 80 wistar rats were divided into two experimental groups randomly: the control group and silicosis group (silica-instilled group) .The two groups have five time points respectively,as 1d,7d,14d,21d, 28d, and eight rats each group. After lightly anesthetized with pentobarbital, rats were received a single intratracheal instillation of 1ml 50mg/ml silica suspension in silica-treated group. In control group, rats were treated in the same way but instillation of 1ml sterilized saline instead. At the 1d, 7d, 14d, 21d, and 28d after establishment of animal models, eight rats in each group were sacrificed, and lungs were removed and stored immediately in liquid nitrogen.2. We measure the serum levels of silicon with indirect atomic absorption spectrometric detection. In the silicon and molybdenum heteropoly acid, grams of molybdenum and silicon atoms in the ratio of 12: 1 (weight ratio of molybdenum and silicon 40: 1), using heteropoly acid "chemical amplification", silicon can form a binary complex acid with molybdate. The content of silicon can be discovered directly by detecting the absorbance of molybdenum organic phase (A) after extracting.3. We take the rat lung tissue at maximum diameter of the right lower lung for Paraffin embedding. The changes of lung histomorphology of rats were observed by HE staining of histological section. I, III type collagens of lung tissue were stained by sirius red. 4. All data are analyzed by SPSS 16.0 for windows software and are expressed by x±s,α= 0.05.Results:1. The staining results of HE and sirius red both proved that the rat model of silicosis was successfully established by intratracheal infusion of silica dust suspension. 2. The serum levels of silicon in 1d, 3d, 7d, 14d, 21d and 28d were significantly higher than that in the control group(P<0.05).3. The expression of collagenⅠin the lung tissue of the model rats in 7d, 14d, 21d and 28d were higher than that in the control group (P<0.05).4. The expression of collagenⅢin the lung tissue of model rats in 14d, 21d and 28d were higher than that in the control group (P<0.05).5. The serum levels of silicon in 1d were significantly higher, showing a continuous increase trend, the changes was much earlier than the expression ofⅠ,Ⅲcollagen; With the increase of serum silicon,Ⅰcollagen,Ⅲcollagen increased gradually.Conclusion: Changes of serum levels of silicon in rats exposed to silica was appeared in the first day after exposed to silica dust, and it is earlier than the expression of collagenⅠand collagenⅢ. The results indicate that there were some value and meaning in the early diagnosis of silicosis by determining silica content of serum.