Effects of sublethal, environmentally relevant concentrations of hexavalent chromium in the gills of Mytilus galloprovincialis.
Hexavalent chromium Cr(VI) is an important contaminant released from both domestic and industrial effluents, and represents the predominant chemical form of the metal in aquatic ecosystems. In the marine bivalve Mytilus galloprovincialis exposure to non-toxic, environmentally relevant concentrations of Cr(VI) was shown to modulate functional parameters and gene expression in both the digestive gland and hemocytes. In this work, the effects of exposure to Cr(VI) (0.1-1-10 μg L(-1) animal(-1) for 96 h) in mussel gills were investigated. Gill morphology and immunolocalization of GSH-transferase (GST), of components involved in cholinergic (AChE and ChAT), adrenergic (TH) and serotoninergic (5-HT(3) receptor) systems, regulating gill motility, were evaluated. Total glutathione content, activities of GSH-related enzymes (glutathione reductase - GSR, GST), of catalase, and of key glycolytic enzymes (phosphofructokinase - PFK and pyruvate kinase - PK) were determined. Moreover, mRNA expression of selected Mytilus genes (GST-π, metallothionein isoforms MT10 and MT20, HSP70 and 5-HT receptor) was assessed by RT-q-PCR. Cr(VI) exposure induced progressive changes in gill morphology and in immunoreactivity to components involved in neurotransmission that were particularly evident at the highest concentration tested, and associated with large metal accumulation. Cr(VI) increased the activities of GST and GSR, and total glutathione content to a different extent at different metal concentrations, this suggesting Cr(VI) detoxication/reduction at the site of metal entry. Cr(VI) exposure also increased the activity of glycolytic enzymes, indicating modulation of carbohydrate metabolism. Significant changes in transcription of different genes were observed. In particular, the mRNA level for the 5-HTR was increased, whereas both decreases and increases were observed for GST-π, MT10, MT20 and HSP70 mRNAs, showing sex- and concentration-related differences. The results demonstrate that Cr(VI) significantly affected functional and molecular parameters in mussel gills, and indicate that this tissue represents the major target of exposure to environmentally relevant concentrations of the metal.
DISTEVA, Dipartimento di Scienze della Terra, della Vita e dell'Ambiente, Università Carlo Bo di Urbino, Italy.
Caterina
C
Ciacci
Cristina
C
Barmo
Gabriella
G
Gallo
Maria
M
Maisano
Tiziana
T
Cappello
Alessia
A
D'Agata
Claudio
C
Leonzio
Angela
A
Mauceri
Salvatore
S
Fasulo
Laura
L
Canesi
D000818:Animals; D002857:Chromium / Q000493:pharmacokinetics / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005880:Gills / Q000033:anatomy & histology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008297:Male; D049878:Mytilus / Q000033:anatomy & histology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic
D012333:RNA, Messenger; D002857:Chromium; C074702:chromium hexavalent ion