Toxic Effects on Oxidative Stress, Neurotoxicity, Stress, and Immune Responses in Juvenile Olive Flounder, Paralichthys olivaceus, Exposed to Waterborne Hexavalent Chromium

Abstract

Juvenile Paralichthys olivaceus were exposed to waterborne hexavalent chromium at various concentrations (0, 0.5, 1.0, and 2.0 mg/L) for 10 days. After chromium exposure, the activities of superoxide dismutase and glutathione S-transferase, which are oxidative stress indicators, were significantly increased; however, the glutathione level was significantly reduced. Acetylcholinesterase activity as a neurotoxicity marker was significantly inhibited upon chromium exposure. Other stress indicators, including plasma cortisol and heat shock protein 70, were significantly increased. The immune response markers (lysozyme and immunoglobulin M) were significantly decreased after chromium exposure. These results suggest that exposure to environmental toxicity in the form of waterborne chromium at concentrations higher than 1.0 mg/L causes significant alterations in antioxidant responses, neurotransmitters, stress, and immune responses in juvenile olive flounders. This study will provide a basis for an accurate assessment of the toxic effects of hexavalent chromium on aquatic organisms.

Keywords: antioxidant responses; hexavalent chromium; immune responses; neurotransmitter; stress responses.

Figure 1

Antioxidant responses of flatfish, Paralichthys olivaceus exposed to the different concentrations of waterborne chromium for 10 days. Values with different superscripts are significantly different in 5 and 10 days (p < 0.05) as determined by Tukey’s multiple range test.

Figure 2

AChE inhibition of flatfish, Paralichthys olivaceus exposed to the different concentrations of waterborne chromium for 10 days. Values with different superscripts are significantly different in 5 and 10 days (p < 0.05) as determined by Tukey’s multiple range test.

Figure 3

Plasma cortisol of flatfish, Paralichthys olivaceus, exposed to the different concentrations of waterborne chromium for 10 days. Values with different superscripts are significantly different in 5 and 10 days (p < 0.05) as determined by Tukey’s multiple range test.

Figure 4

HSP 70 of flatfish, Paralichthys olivaceus, exposed to the different concentrations of waterborne chromium for 10 days. Values with different superscripts are significantly different in 5 and 10 days (p < 0.05) as determined by Tukey’s multiple range test.

Figure 5

Immune responses of flatfish, Paralichthys olivaceus exposed to the different concentrations of waterborne chromium for 10 days. Values with different superscripts are significantly different in 5 and 10 days (p < 0.05) as determined by Tukey’s multiple range test.