Cadmium Accumulation and mRNA Expression Associated with Detoxification in Various Organs of Black Seabream (Acanthopagrus schlegelii) Exposed to Cadmium-contaminated Diet

Abstract

Cadmium toxicity is proportional to its ionic concentration, and with long-term exposure, it interferes with ion regulation to maintain homeostasis and affects growth, reproduction, development, behavior, and immune and endocrine systems in organisms. Particularly, cadmium has a long residence time in the body, and if continuously absorbed, it accumulates in tissues, causing bioconcentration. Here, black seabream (Acanthopagrus schlegelii) was exposed to a cadmium-treated diet to investigate cadmium accumulation and mRNA expression of metallothionein (MTII) and heat shock protein (HSP90). The tissue-specific cadmium concentration showed a significant correlation with cadmium concentration and time in all treated tissues except the muscle. Cadmium accumulation in each organ decreased as follows: intestine > liver > gill > muscle. The MT II mRNA level initially increased in the intestine, before decreasing with time, different from the pattern in the other organs. In contrast, the liver showed an increasing trend of MT II mRNA level after the initial increase in the intestine. An increase in the MT II mRNA level in the gill was observed only under high cadmium concentration. Besides, the HSP90 mRNA level initially increased in the intestine and liver, but decreased with time, similar to that in the control group on day 28. mRNA expression of both MT II and HSP90 was observed in the gill and no significant difference was observed in the muscle. The results suggest that the cadmium accumulation pattern with dietary exposure to cadmium was different in each organ in relation to the protective genes metallothionein (MT II) and heat shock protein (HSP90).