Hexavalent chromium-induced multiple biomarker responses in liver and kidney of goldfish, Carassius auratus

Abstract

Hexavalent chromium [Cr (VI)] is a constituent of chromite ore. Although it is known to have several industrial and technological applications, its release into the aquatic environment as a result of chemical spill or inadequate waste discharge may hamper the health of aquatic organisms. In this study, we have investigated the effects of Cr (VI) on multiple biomarkers responses in goldfish under subchronic exposure conditions. Laboratory-acclimatized fish were exposed to 4.25 ppm and 8.57 ppm Cr (VI) for four weeks using a continuous flow-through system. During exposure, fish samples were collected on a weekly basis and analyzed for multiple biomarkers including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), metallothionein (MT), and total protein in liver and kidney. Study results indicated that the CAT activity and total protein levels in Cr (VI) - treated goldfish did not significantly differ (P > 0.05) from their respective controls during experimentation. However, highly significant up-regulations (P < 0.05) of SOD, GPx, and MT expression in Cr (VI) - treated goldfish were recorded at different exposure times depending on Cr (VI) concentration, test organ, and/or biomarker of interest. For example, significantly higher liver GPx levels were found at weeks 2 and 3 in the 4.25 ppm concentration, and at weeks 3 and 4 in the 8.57 ppm, while kidney GPx levels were significantly higher at weeks 1, 2 and 3 in the 4.25 ppm concentration, and at weeks 2, 3 and 4 in the 8.57 ppm concentration. In summary, Cr (VI)-induced oxidative stress was characterized by statistically significant increases in SOD, GPx, and MT expression in goldfish tissues; with the kidney showing a relatively higher sensitivity to Cr (VI) toxicity compared with the liver.

Fig.1

Catalase (CAT) activity in Carassius auratus liver exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates.

Fig. 2

Catalase (CAT) activity in Carassius auratus kidney exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates.

Fig. 3

Superoxide dismutase (SOD) activity in Carassius auratus liver exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 4

Superoxide dismutase (SOD) activity in Carassius auratus kidney exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 5

Glutathione peroxidase (GPx) activity in Carassius auratus liver exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 6

Glutathione peroxidase (GPx) activity in Carassius auratus kidney exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 7

Metallothionein levels in Carassius auratus liver exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 8

Metallothionein levels in Carassius auratus kidney exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates. *Significantly different from the control according to Dunnett's multiple comparison test.

Fig. 9

Total protein levels in Carassius auratus liver exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates.

Fig.10

Total protein levels in Carassius auratus kidney exposed to Cr (VI) (5% and 10% of 96hr-LC₅₀) for a four week time period. Each point represents a mean value ± SD of three replicates.