Losses of immunoreactive parvalbumin amacrine and immunoreactive alphaprotein kinase C bipolar cells caused by methylmercury chloride intoxication in the retina of the tropical fish Hoplias malabaricus.
To quantify the effects of methylmercury (MeHg) on amacrine and on ON-bipolar cells in the retina, experiments were performed in MeHg-exposed groups of adult trahiras (Hoplias malabaricus) at two dose levels (2 and 6 microg/g, ip). The retinas of test and control groups were processed by mouse anti-parvalbumin and rabbit anti-alphaprotein kinase C (alphaPKC) immunocytochemistry. Morphology and soma location in the inner nuclear layer were used to identify immunoreactive parvalbumin (PV-IR) and alphaPKC (alphaPKC-IR) in wholemount preparations. Cell density, topography and isodensity maps were estimated using confocal images. PV-IR was detected in amacrine cells in the inner nuclear layer and in displaced amacrine cells from the ganglion cell layer, and alphaPKC-IR was detected in ON-bipolar cells. The MeHg-treated group (6 microg/g) showed significant reduction of the ON-bipolar alphaPKC-IR cell density (mean density = 1306 +/- 393 cells/mm2) compared to control (1886 +/- 892 cells/mm2; P < 0.001). The mean densities found for amacrine PV-IR cells in MeHg-treated retinas were 1040 +/- 56 cells/mm2 (2 microg/g) and 845 +/- 82 cells/mm2 (6 microg/g), also lower than control (1312 +/- 31 cells/mm2; P < 0.05), differently from the data observed in displaced PV-IR amacrine cells. These results show that MeHg changed the PV-IR amacrine cell density in a dose-dependent way, and reduced the density of alphaKC-IR bipolar cells at the dose of 6 microg/g. Further studies are needed to identify the physiological impact of these findings on visual function.
Bonci
D M O
DM
Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, São Paulo, SP, Brazil. dbonci@usp.br
Lima
S M A de
SM
Grötzner
S R
SR
Ribeiro
C A Oliveira
CA
Hamassaki
D E
DE
Ventura
D F
DF
D025042:Amacrine Cells / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D005399:Fishes / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000633:toxicity*; D010320:Parvalbumins / Q000187:drug effects* / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000187:drug effects* / Q000378:metabolism; D051245:Retinal Bipolar Cells / Q000187:drug effects* / Q000378:metabolism
D008767:Methylmercury Compounds; D010320:Parvalbumins; D051571:Protein Kinase C-alpha; C004925:methylmercuric chloride