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Zn>Cd &Hg>Cu Pathiratne et al(2009) and Ghedtra et al (2010) Richard (1994) -MT induction -liver : Hg > Ag> Cu > Zn. Metallothionein - a potential biomarker to assess the metal contamination in marine fishes-A review Metal Transcription -of MT genes MT synthesis •Cd can induce MT expression in Fishes. (Chen et al. 2005, Rovira et al. 2005, Choi et al. 2007) •MT transcript proteins -bivalent metal - Zn, Cu, Pb, Fe, Co and Hg. ( Ikebuchi et al. 1986; Carginale et al. 1998; Riggio et al. 2003 ) • Thiele in 1992- MT gene expression ὰ Metal concentration. •4 MT genes-common promoter-several MREs- which binds to metal transcription factors- synthesis of MT.(Kling and Olsson in 1993). Factors Affecting the Metallothionein Estimations age Sexual maturity- max variation-female Olsson et al ( 1987) - Rainbow Trout –hepatic MT levels Sex Liv er Musc le Kidn ey brai n Skin Gill s Tissue type Route of exposure and experimental conditions MT Leve ls fish speci es tissue physiolo gy experimenta l condition s • Chowdhury et al (2005) -Rainbow trout -sub lethal concentration - waterborne Cd (0 or 3 μg/L) or dietary Cd (0 or 500 mg/kg dry wt) -30 days • Waterborne exposure group- highest MT- kidney - Gills – liver. • Dietary exposure group-kidney >> cecae and posterior intestine > liver and stomach > midintestine > gills. Exogenous and endogenous substances Experimental problems with MTs Olsson 1996 Metal Type Seasonal variations Future prospects 1. Inorganic Hg Invitro studies Cell culture Invivo influence Not clear Organic-mercury complex 2. Standardization of methods 3.Different methodology used by researchers Thiele D J (1992).Metal Regulated Transscription in Eukaryotes. Nucleic Acid Research.210;1183-1188. Kling, P. & Olsson. P. E. (1993). Metal regulation of the rainbow trout metallothionein-A gene. In: proceedings of the Seventh International Symposium on Responses of Marine Organisms to Pollutants. Geroge S.G.,Hadgson P.A.,Tybler .P.,Tedd.K.,(1996).Inducability of Metallothionein mRNA expression and Cadmium tolerance in larva of teleosts the turbot (Scophthalmus maximus). Fundamental Application of Toxicology 33:91-99. (George et al.,1996) Referenc e Vijaya * and R. Jayakumar** *Research Scholar, **Assistant Professor, Department of Environmental Science, GITAM University, Bengaluru Campus, Nagadenahalli-562 163. KARNATAKA. E-mail:[email protected] MT as Biomarker •Ubiquitous , stable & inducible proteins, Mw 6-8kDa, pI-8.3 •High cysteine content (20-30%) - 61 amino acids - no aromatic amino acids. • Binds to metals - metal thiolate bonds. •Metal homeostasis –Zn ,Cu & detoxification – Cd, Hg, Pt, Ag Introductio n Metallothionein (MTs) Cd Higher affinity to MTs tan Zn Displace Zn from MT binding site (Hollis L.C and C.M.Wood, 2001) Maximum induction MTs in Tilapia 2mg/kg of Cd No further change (Y.F.Ueng et al. 1996)

metallothionein -Biomarker

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Zn>Cd &Hg>Cu

Pathiratne et al(2009) and Ghedtra et al (2010) Richard (1994) -MT induction -liver : Hg > Ag> Cu > Zn.

Metallothionein - a potential biomarker to assess the metal contamination in marine fishes-A review

Metal

Transcription -of MT genes

MT synthesis

•Cd can induce MT expression in Fishes. (Chen et al. 2005, Rovira et al. 2005, Choi et al. 2007) •MT transcript proteins -bivalent metal - Zn, Cu, Pb, Fe, Co and Hg. ( Ikebuchi et al. 1986; Carginale et al. 1998; Riggio et al. 2003 )• Thiele in 1992- MT gene expression ὰ Metal concentration.•4 MT genes-common promoter-several MREs- which binds to metal transcription factors-synthesis of MT.(Kling and Olsson in 1993).

Factors Affecting the Metallothionein Estimations

age

Sexual maturity- max variation-femaleOlsson et al ( 1987) - Rainbow Trout –hepatic MT levels

Sex

Liver

Muscle

Kidney

brainSkin

Gills

Tissue type

Route of exposure and experimental conditions

MT Levels

fish species

tissue physiology

experimental conditions

• Chowdhury et al (2005) -Rainbow trout -sub lethal concentration -waterborne Cd (0 or 3 μg/L) or dietary Cd (0 or 500 mg/kg dry wt) -30 days• Waterborne exposure group- highest MT- kidney - Gills – liver.• Dietary exposure group-kidney >> cecae and posterior intestine > liver and stomach > midintestine > gills.

Exogenous and endogenous substances

Experimental problems with MTs

Olsson 1996

Metal Type

Seasonal variations

Future prospects

1. Inorganic Hg Invitro studies Cell culture

Invivo influence

Not clear

Organic-mercury complex

2. Standardization of methods 3.Different methodology used by researchers

•Thiele D J (1992).Metal Regulated Transscription in Eukaryotes. Nucleic Acid Research.210;1183-1188.•Kling, P. & Olsson. P. E. (1993). Metal regulation of the rainbow trout metallothionein-A gene. In: proceedings of the Seventh International Symposium on Responses of Marine Organisms to Pollutants.•Geroge S.G.,Hadgson P.A.,Tybler .P.,Tedd.K.,(1996).Inducability of Metallothionein mRNA expression and Cadmium tolerance in larva of teleosts the turbot (Scophthalmus maximus).Fundamental Application of Toxicology 33:91-99.•Singh M R. (2007). Impurities-heavy metals: IR prespective.(George et al.,1996)

Reference

Vijaya * and R. Jayakumar** *Research Scholar, **Assistant Professor, Department of Environmental Science, GITAM University, Bengaluru Campus, Nagadenahalli-562 163. KARNATAKA. E-mail:[email protected]

MT as Biomarker

•Ubiquitous , stable & inducible proteins, Mw 6-8kDa, pI-8.3•High cysteine content (20-30%) - 61 amino acids - no aromatic amino acids.• Binds to metals - metal thiolate bonds.•Metal homeostasis –Zn ,Cu & detoxification – Cd, Hg, Pt, Ag

Introduction

Metallothionein (MTs)

Cd Higher affinity to MTs tan Zn

Displace Zn from MT binding site

(Hollis L.C and C.M.Wood, 2001)

Maximum induction

MTs in Tilapia 2mg/kg of Cd No further change

(Y.F.Ueng et al. 1996)