[The expression of lung nitric oxide synthase in rat exposed to silica].
OBJECTIVE
To evaluate the time-effect of silica on the expression of lung tissue nitric oxide synthase (NOS) in early inflammatory damage stage of silicotic rat.


METHODS
Animal models were established by direct tracheal instillation of silica into rat lungs. Total NOS and induced NOS (iNOS) activities in bronchoalveolar lavage fluid (BALF) were assayed. The expression of iNOS protein in paraffin-embedded lung sections with Streptavidin/peroxidase (SP) immunohistochemistry were measured by tissue microarray and Image-Pro Plus.


RESULTS
Most of the expression of iNOS was in the cytoplasm of macrophages and neutrophils. iNOS integrated optical density (IOD) of lung tissue increased 1.47 x 10(5) and 2.73 x 10(5) more respectively in silicatreated rats 3, 7 days after exposure than in control rats (P < 0.05), and decreased 1.11 x 10(5) more 28 days after exposure (P < 0.01). The activities of iNOS in BALF increased by 0.86, 1.89 and 0.92 U/ml respectively 3, 7, 14 days after exposure (P < 0.05 or P < 0.01). The activities of total NOS in BALF increased by 1.43, 2.05, 2.61 and 2.19 U/ml respectively 1, 3, 7, 14 days after exposure (P < 0.05 or P < 0.01).


CONCLUSIONS
After silica instillation, the iNOS-positive cells in rat lung tissue were mostly macrophages and neutrophils. There is a parabolic changing trend in the level of expression of lung iNOS during 1 - 28 day exposure to silica.
Wang
Shi-xin
SX
College of Bioengineering, Chongqing University, Chongqing 400044, China.
Zhang
Xi-zheng
XZ
Cai
Shao-xi
SX
Du
Hai-ke
HK
Zhang
Shi-wu
SW
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D005260:Female; D007150:Immunohistochemistry; D008168:Lung / Q000187:drug effects / Q000201:enzymology; D008297:Male; D023421:Models, Animal; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012822:Silicon Dioxide / Q000633:toxicity*
D012822:Silicon Dioxide; D019001:Nitric Oxide Synthase