The relationship between reproductive status and metallothionein mRNA expression in the common killifish, Fundulus heteroclitus

Metallothionein (MT), a ubiquitously distributed cysteine-rich metal binding protein, is considered to play an essential role in the regulation of intracellular metals and may serve as a defense mechanism as well as a biomarker of environmental exposure to toxic metals. In this study, basal expression of MT mRNA was characterized in male and female killifish Fundulus heteroclitus during non-spawning and spawning seasons. Hepatic, gill, and intestinal MT mRNA (copy number per μg total RNA) was assessed by reverse-transcriptase polymerase chain reaction (RT-PCR) and electrochemiluminescence (ECL). There were no observed differences in MT mRNA expression between male and female killifish during either season. The median MT copy numbers for both non-spawning and spawning killifish decreased in the order of liver>intestine>gill. In addition, there were no significant differences in liver, gill and intestine tissue MT mRNA copy numbers within each season. However, a significant increase in gill and intestine MT mRNA induction was observed in spawning compared to non-spawning killifish (p