Expression of metallothionein gene at different time in testicular interstitial cells and liver of rats treated with cadmium.
OBJECTIVE
Rodent testes are generally more susceptible to cadmium (Cd)-induced toxicity than liver. To clarify the molecular mechanism of Cd-induced toxicity in testes, we compared metallothionein (MT) gene expression, MT protein accumulation, and Cd retention at different time in freshly isolated testicular interstitial cells and liver of rats treated with Cd.


METHODS
Adult male Sprague-Dawley rats weighing 250-280 g received a s.c injection of 4.0 micromol Cd/kg and were euthanized by CO(2) asphyxiation 1 h, 3 h, 6 h, or 24 h later. Tissue was sampled and testicular interstitial cells were isolated. There were three replicates per treatment and 3 animals per replicate for RNA analyses, others, three replicates per treatment and one animal per replicate. MT1 and MT2 mRNA levels were determined by semi-quantitative RT-PCR analysis followed by densitometry scanning, and MT was estimated by the enzyme-linked immunosorbent assay (ELISA) method. Cadmium content was determined by atomic absorption spectrophotometry. The same parametersd were also analyzed in the liver, since this tissue unquestionably accumulate MT.


RESULTS
The rat testis expressed MT1 and MT2, the major isoforms. We also found that untreated animals contained relatively high basal levels of both isoform mRNA, which were increased after Cd treatment in liver and peaked at 3 h, followed by a decline. In contrast, the mRNA levels in interstitial cells peaked at 6 h. Interestingly, the induction of MT1 mRNA was lower than MT2 mRNA in liver of rat treated with Cd, but it was opposite to interstitial cells. Cd exposure substantially increased hepatic MT (3.9-fold increase), but did not increase MT translation in interstitial cells.


CONCLUSIONS
Cd-induced expression of MT isoforms is not only tissue dependent but also time-dependent. The inability to induce the metal-detoxicating MT-protein in response to Cd, may account for a higher susceptibility of testes to Cd toxicity and carcinogenesis compared to liver.
Ren
Xu-Yi
XY
Department of Biochemistry and Molecular Biology, Second Military Medical University, Shanghai 200433, China. renxuyi2003@163.com
Zhou
Yong
Y
Zhang
Jian-Peng
JP
Feng
Wei-Hua
WH
Jiao
Bing-Hua
BH
D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000633:toxicity*; D015870:Gene Expression / Q000187:drug effects; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000502:physiology*; D008297:Male; D008668:Metallothionein / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013737:Testis / Q000166:cytology / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects
D012333:RNA, Messenger; D002104:Cadmium; D008668:Metallothionein