title: In vitro free radical scavenging activity of hepatic metallothionein induced in an Indian freshwater fish, Channa punctata Bloch.
abstract: Mammalian metallothioneins (MT) have been reported to scavenge free radicals. There is no experimental evidence to show that fish MT has a similar property. In the present study cadmium-induced MT (Cd-MT) from the liver of an Indian freshwater fish Channa punctata Bloch was investigated for its free radical scavenging activity using three different in vitro assays. Exposure to cadmium chloride (0.2 mg/kg body weight; three doses on alternate days) resulted in a marked induction of Cd-MT in liver. Only a single isoform of Cd-MT was found to be induced. Molecular weight of Cd-MT was found to be 14 kDa as deduced by SDS-PAGE analysis. The purified Cd-MT effectively scavenged the following free radicals: superoxide radical (O2*-), 2,2'-azinobis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS*+) and 1,1-diphenyl-picrylhydrazyl radical (DPPH*). The radical scavenging effect was found to be concentration-dependent. Also, the purified MT exhibited an inhibitory effect on ferric nitrilotriacetate (Fe-NTA) induced oxidative DNA damage in vitro. The cysteine residues of MT are proposed to be the main candidate for its radical scavenging activity. Findings of the present study strongly suggest a free radical scavenging role for fish MT. Present study adds to the little existing knowledge about fish MT and its possible biological functions.
authors.affiliation: Department of Medical Elementology and Toxicology, Jamia Hamdard (Hamdard University), New Delhi 110062, India.
authors.forename: Fahim
authors.initials: F
authors.lastname: Atif
authors.forename: Manpreet
authors.initials: M
authors.lastname: Kaur
authors.forename: Seema
authors.initials: S
authors.lastname: Yousuf
authors.forename: Sheikh
authors.initials: S
authors.lastname: Raisuddin
mesh_terms: D000818:Animals; D052160:Benzothiazoles; D001713:Biphenyl Compounds / Q000737:chemistry; D002104:Cadmium / Q000032:analysis / Q000494:pharmacology; D004247:DNA / Q000737:chemistry; D004249:DNA Damage / Q000187:drug effects; D005290:Ferric Compounds / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006834:Hydrazines / Q000737:chemistry; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008668:Metallothionein / Q000737:chemistry* / Q000302:isolation & purification; D008970:Molecular Weight; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009571:Nitrilotriacetic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D009573:Nitrites / Q000737:chemistry; D010473:Perciformes / Q000378:metabolism*; D010851:Picrates; D013451:Sulfonic Acids / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D001713:Biphenyl Compounds; D005290:Ferric Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D006834:Hydrazines; D009573:Nitrites; D010851:Picrates; D013451:Sulfonic Acids; D002104:Cadmium; D013481:Superoxides; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D004247:DNA; D008668:Metallothionein; C004931:1,1-diphenyl-2-picrylhydrazyl; D009571:Nitrilotriacetic Acid; C020326:ferric nitrilotriacetate