Short-term exposure of Nile Tilapia (Oreochromis niloticus) to mercury: histopathological changes, mercury bioaccumulation, and protective role of metallothioneins in different exposure routes.
To investigate effects of short-term mercury (Hg) exposure in tilapia (Oreochromis niloticus) including histopathological changes, Hg bioaccumulation, and protective role of metallothionein (MT) in different exposure routes, adult tilapias were intraperitoneally injected, orally intubated, or semistatically exposed to 0.5, 1, 2, 5 µg/g mercuric chloride. Histopathology, autometallography (AMG), inductive coupled plasma-atomic emission spectrometry (ICP-AES), and MT immunohistochemistry were determined at 0, 3, 6, 9, 12, and 15 days postexposure. Microscopic lesions were observed in the kidney, hepatopancreas, spleen, and intestine. AMG positive grains were found in renal tubule epithelium, melanomacrophage centers (MMCs), and intestinal epithelium of treated tilapias. Hg concentrations measured by ICP-AES in abdominal visceral organs were significantly higher than in other organs. All exposure routes caused lesions of increasing severity and Hg accumulations in a dose-dependent manner. Semistatic groups produced the highest intensity of lesions, AMG positive staining, as well as total Hg concentrations. Positive MT expression in renal tubule epithelium, pancreatic acini, and splenic MMCs was observed only in semistatic groups. The semistatic exposure route demonstrated the most significant microscopic lesions, Hg bioaccumulation, and MT expression.
Department of Veterinary Pathology, Chulalongkorn University, Bangkok, Thailand.
Theerayuth
T
Kaewamatawong
Kasem
K
Rattanapinyopituk
Aranya
A
Ponpornpisit
Nopadon
N
Pirarat
Suthep
S
Ruangwises
Anudep
A
Rungsipipat
D000818:Animals; D023681:Cichlids / Q000378:metabolism*; D007668:Kidney / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D008099:Liver / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D008628:Mercury / Q000493:pharmacokinetics* / Q000633:toxicity*; D008668:Metallothionein / Q000378:metabolism*; D020011:Protective Agents / Q000378:metabolism*; D011897:Random Allocation; D013057:Spectrum Analysis; D013154:Spleen / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D014018:Tissue Distribution; D023382:Toxicity Tests, Acute
D020011:Protective Agents; D008668:Metallothionein; D008628:Mercury