Effects of cadmium on hepatocellular DNA damage, proto-oncogene expression and apoptosis in rats.
OBJECTIVE
To study the effects of cadmium on hepatocellular DNA damage, expression of proto-oncogenes c-myc, c-fos, and c-jun as well as apoptosis in rats.


METHODS
Cadmium chloride at the doses of 5, 10, and 20 micromol/kg was given to rats by i.p. and there were 5 male SD rats in each group. Hepatocellular DNA damage was measured by single cell gel electrophoresis (or comet assay), while expression of proto-oncogenes c-myc, c-fos, and c-jun in rat hepatocytes were measured by Northern dot hybridization. C-Myc, c-Fos, and c-Jun were detected with immuno-histochemical method. Hepatocellular apoptosis was determined by TUNEL (TdT-mediated dUTP Nick End Labelling) and flow cytometry.


RESULTS
At the doses of 5, 10, and 20 micromol/kg, cadmium chloride induced DNA damage in rat hepatocytes and the rates of comet cells were 50.20%, 88.40%, and 93.80%, respectively. Results also showed an obvious dose-response relationship between the rates of comet cells and the dose of cadmium chloride (r = 0.9172, P < 0.01). Cadmium chloride at the doses of 5, 10, and 20 micromol/kg induced expression of proto-oncogenes c-myc, c-fos, and c-jun. The positive brown-yellow signal for c-myc, c-fos, and c-jun was mainly located in the cytoplasm of hepatocytes with immunohistochemical method. TUNEL-positive cells were detected in cadmium-treated rat livers. Apoptotic rates (%) of cadmium-treated liver cells at the doses of 5, 10, and 20 micromol/kg were (17.24 +/- 2.98), (20.58 +/- 1.35), and (24.06 +/- 1.77) respectively, being significantly higher than those in the control. The results also displayed an obvious dose-response relationship between apoptotic rates and the dose of cadmium chloride (r = 0.8619, P < 0.05).


CONCLUSIONS
Cadmium at 5-20 micromol/kg can induce hepatocellular DNA damage, expression of proto-oncogenes c-myc, c-fos, and c-jun as well as apoptosis in rats.
Yu
Ri-An
RA
Department of Occupational and Environmental Health, Shool of Public Health, Guangdong Pharmaceutical University, Guangzhou 510310, Guangdong, China. yurian.tj@163.com
He
Ling-Fei
LF
Chen
Xue-Min
XM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002104:Cadmium / Q000633:toxicity*; D004249:DNA Damage; D005786:Gene Expression Regulation / Q000187:drug effects*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D016271:Proto-Oncogene Proteins c-myc; D002104:Cadmium