|ZFIN ID: ZDB-PUB-071009-1|
Selenomethionine reduces visual deficits due to developmental methylmercury exposures
Weber, D.N., Connaughton, V.P., Dellinger, J.A., Klemer, D., Udvadia, A., and Carvan, MJ 3rd.
|Source:||Physiology & behavior 93(1-2): 250-260 (Journal)|
|Registered Authors:||Carvan III, Michael J., Connaughton, Victoria P., Udvadia, Ava J., Weber, Dan|
|Keywords:||Behavioral toxicology, Bipolar cells, Mercury, Retina, Selenium, Visual response, Voltage-gated potassium currents, Zebrafish|
|PubMed:||17905328 Full text @ Physiol. Behav.|
Weber, D.N., Connaughton, V.P., Dellinger, J.A., Klemer, D., Udvadia, A., and Carvan, MJ 3rd. (2008) Selenomethionine reduces visual deficits due to developmental methylmercury exposures. Physiology & behavior. 93(1-2):250-260.
ABSTRACTDevelopmental exposures to methylmercury (MeHg) have life-long behavioral effects. Many micronutrients, including selenium, are involved in cellular defenses against oxidative stress and may reduce the severity of MeHg-induced deficits. Zebrafish embryos (<4 h post fertilization, hpf) were exposed to combinations of 0.0-0.30 muM MeHg and/or selenomethionine (SeMet) until 24 hpf then placed in clean medium. Fish were tested as adults under low light conditions ( approximately 60 muW/m(2)) for visual responses to a rotating black bar. Dose-dependent responses to MeHg exposure were evident (ANOVA, P<0.001) as evidenced by reduced responsiveness, whereas SeMet did not induce deficits except at 0.3 muM. Ratios of SeMet:MeHg of 1:1 or 1:3 resulted in responses that were indistinguishable from controls (ANOVA, P<0.001). No gross histopathologies were observed (H&E stain) in the retina or optic tectum at any MeHg concentration. Whole-cell, voltage-gated, depolarization-elicited outward K(+) currents of bipolar cells in intact retina of slices adult zebrafish were recorded and outward K(+) current amplitude was larger in bipolar cells of MeHg-treated fish. This was due to the intense response of cells expressing the delayed rectifying I(K) current; cells expressing the transient I(A) current displayed a slight trend for smaller amplitude among MeHg-treated fish. Developmental co-exposure to SeMet reduced but did not eliminate the increase in the MeHg-induced I(K) response, however, I(A) responses increased significantly over MeHg-treated fish to match control levels. Electrophysiological deficits parallel behavioral patterns in MeHg-treated fish, i.e., initial reactions to the rotating bar were followed by periods of inactivity and then a resumption of responses.
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