Effect of chromate and chromite in rainbow trout (Oncorhynchus mykiss) at environmentally relevant concentrations

The Ring of Fire is a region in the James Bay Lowlands of northern Ontario that houses a rich deposit of chromite and is slated for mining development. The goals of this study were to better understand the relative effects of Cr(VI) to Cr(III) in rainbow trout, identify potential protein biomarkers to distinguish between Cr(VI) and Cr(III) exposure, and determine potential biomarkers for chromium exposure at concentrations below observable effect levels. Proteomic analysis on the fish plasma showed no difference in Cr(VI) and Cr(III) exposure across all concentrations and between chromium species. Proteins associated with hepatocellular carcinoma and cardiomyopathy (Trim21, Slc8a1, Myh4 and Myh6) all decreased in abundance in response to Cr(VI) and Cr(III) exposure, and decreases in these proteins are associated with adverse outcomes. Proteomic analysis of the trout livers also showed no difference in Cr(VI) and Cr(III) exposure for all concentrations and between chromium species. Again, all proteins decreased in abundance, with Gys2 being associated with hepatocellular carcinoma and it was the only protein with a notable adverse outcome. We hope that this study will advance knowledge on chromium toxicity in fish and protect all that inhabit the Ring of Fire region of Canada.