Metallothionein from Pseudosciaena crocea: expression and response to cadmium-induced injury in the testes.

Metallothioneins (MTs) are a family of stress proteins that are involved in the process of detoxification and anti-oxidation. Previous studies have focused mostly on the expression and functions of MTs in the non-reproductive tissues of aquatic vertebrates. However, there have been only a few reports regarding the functions of MTs in the reproductive tissues of such vertebrates. In order to investigate the function of MTs during spermatogenesis in Pseudosciaena crocea, reverse-transcription polymerase chain reaction (PCR) and rapid amplification of cDNA ends were performed to obtain the P. crocea MT complete cDNA sequence from the total RNA of the testes for the first time. MT was detected in the liver, kidneys, testes, spleen, gill and muscle of P. crocea by tissue-specific expression analysis. Meanwhile, immunohistochemistry staining indicated that the MT protein was localized in germ cells, Sertoli cells and the peripheral connective tissues in P. crocea testes. Furthermore, acute toxicity tests were conducted with cadmium (Cd) to determine the 96 h-medial lethal concentration value. The toxic effects of Cd on the microstructure and ultrastructure of the testes were observed. In addition, the changes in MT mRNA expression levels in the testes after Cd exposure were measured using real-time quantitative PCR. Consequently, we suggest that MTs play an important role in spermatogenesis and testes protection against Cd toxicity in P. crocea.