The interplay between thiol-compounds against chromium (VI) in the freshwater green alga Monoraphidium convolutum: Toxicology, photosynthesis, and oxidative stress at a glance

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• 作者：R. Takami^a ; ¹ ; J.V. Almeida^b ; ¹ ; C.V. Vardaris^a ; P. Colepicolo^b ; M.P. Barros^a ; ^{marcelo.barros@cruzeirodosul.edu.br}
• 关键词：APX ; ascorbate peroxidase ; CHLa ; chlorophyll a ; (CHLa ; PROT) ; chlorophyll a ; protein ratio ; Cr(VI) ; chromium (VI) forms ; Cys ; cystein ; DTNB ; 5 ; 5&prime ; -dithiobis(2-nitrobenzoic acid) ; ETR ; electron transfer rate ; GR ; glutathione reductase ; GSH ; reduced glut
• 刊名：Aquatic Toxicology
• 出版年：2012
• 期刊代码：19_0166445x
• 类别：abs
• 出版时间：15 August, 2012
• 卷：118-119
• 期：Complete
• 页码：80-87
• 文件大小：690 K

摘要

In this paper, the multifaceted Cr(VI) toxicity over the freshwater green alga Monoraphidium convolutum was assessed by concomitantly monitoring thiol-dependent redox balances, photosynthesis activity and growth-survival scores. Control group showed exponential growth rate at (5.78 卤 0.29) division/day until 8th day with linear increasing chlorophyll a/protein ratios (CHLa/PROT) throughout the period. Cultures of M. convolutum were exposed for 5 days to Cr(VI) concentrations from 0 up to 100 mg/L showing that CHLa/PROT ratios were sensibly affected, in agreement to the calculated LC_50,48h (5.38 卤 0.72) mg/L from the concentration-response curve of cell mortality after 48 h. Regarding photosynthesis effects, Cr(VI) concentrations >1.0 mg/L showed significant increases in short-term (after 2 h) electron transfer rates (ETR) and quantum yields of photosystem II (桅_PSII), followed by subsequent decline of both parameters after 48 and 72 h. Biochemical analyses showed that maximal GSH concentrations in algal cultures were observed upon 1 mg Cr(VI)/L and higher dichromate concentrations dramatically increased the activity of antioxidant GSH-dependent enzymes ascorbate peroxidase and glutathione reductase. However, no variation was observed in the cellular GSH levels, whereas GSSG and lipid peroxidation indexes abruptly increased upon 10 mg Cr(VI)/L exposure. Altogether, plant physiology, photosynthesis and biochemical data suggest that the GSH-dependent antioxidant system is capable to sustain M. convolutum viability through efficient photosynthesis activity and adequate antioxidant responses up to Cr(VI) concentrations of 1.0 mg/L, when redox unbalances were first evidenced.