Toxicity of mercuric chloride, when combined with ionic and nanoparticulate silver on Artemia salina: Growth, fatty acid composition, oxidative stress, and lipid peroxidation

Abstract

This study assessed the individual and binary toxic effects of inorganic mercury (Hg) plus total dissolved Ag (Ag), or silver nanoparticles (Ag NPs), on immobilization, fatty acid composition, and oxidative stress of Artemia salina nauplii, as an aquatic animal model. The acute toxicity tests revealed that the immobilization of nauplii exposed to 510-9 M, 2.510-8 M, and 510-8 M of Hg as HgCl2 decreased in the presence of 110-4 M of Ag NPs or dissolved Ag as AgNO3. The median effective concentration (EC50) of Hg increased from 4.510-8 M to 910-8 M (two-fold) in the presence of Ag (Hg+Ag). Both Ag NPs and Ag decreased the immobilization of nauplii and diminished the oxidative stress and lipid peroxidation induced by Hg. Total amounts of saturated fatty acids (∑SFA) in Hg and Hg+Ag increased compared with the control, but this increase was significantly (P < 0.05) lower in Hg+Ag than in Hg. Total amounts of monounsaturated (∑MUFA), polyunsaturated (∑PUFA), and the ratio of unsaturated to saturated fatty acids (Unsat./Sat.) decreased compared with the control, however, this reduction was significantly (P < 0.05) smaller for ∑PUFA in Hg+Ag than Hg. In Hg+Ag NPs co-exposure, ∑SFA and the Unsat./Sat. ratio showed no significant (P < 0.05) change compared with the control. However, MUFA exhibited a significantly (P < 0.05) increased response and the PUFA decreased compared with the control, but was significantly (P < 0.05) higher than that in Hg. A decline of superoxide dismutase (SOD) and catalase (CAT) activity in nauplii due to exposure to mercury alone was mitigated in the presence of Ag or Ag NPs. The thiobarbituric acid reactive substance also decreased in the Hg+Ag and Hg+Ag NPs treatments. The toxicity effect of the treatments was in the order of Hg > Hg+Ag > Hg+Ag NPs revealing the antagonistic effect of Ag or Ag NPs on Hg toxicity, with the amelioration the greatest in the presence of Ag NPs.