Effects of short-term copper exposure on gill structure, metallothionein and hypoxia-inducible factor-1alpha (HIF-1alpha) levels in rainbow trout (Oncorhynchus mykiss).
Rainbow trout (Oncorhynchus mykiss) were exposed to 1.65 microM of waterborne copper for 24 h. Fish were then transferred to metal-free water. Metallothionein mRNA induction in rainbow trout liver and gill tissue, hypoxia-inducible factor-1 (HIF-1alpha) accumulation in gill tissue and arithmetic mean thickness of gill epithelium (Har) were determined at 4 and 24h of exposure as well as 48 h after transfer to metal-free water. The arithmetic mean distance from water to blood was significantly elevated after both 4 and 24 h of exposure (Har was 4.67 and 4.66 microm, respectively in exposed fish, compared to 3.81 and 3.62 microm for the corresponding control fish). During the 48 h recovery Har returned towards the control values; the recovery value of 4.21 microm was significantly lower than values during exposures. There was also a significant increase in gill metallothionein mRNA levels after the 4 h exposure with MT/GAPDH ratio of 1.288 versus the control value of 0.988. In liver, metallothionein induction was not observed. HIF-1alpha protein showed an increased accumulation in gills after 4 h, with the HIF-1alpha/alpha-tubulin ratio of 0.562 being significantly higher than the 24 h exposure value of 0.232. These results suggest that exposure to copper for four hours causes hypoxia in the gill epithelium, which is adequate for the activation of HIF-1alpha.
van Heerden
Daléne
D
School for Environmental Sciences and Development, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa. drkdvh@puk.ac.za
Vosloo
André
A
Nikinmaa
Mikko
M
D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D001837:Body Weights and Measures; D003300:Copper / Q000633:toxicity*; D005880:Gills / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D023382:Toxicity Tests, Acute; D014157:Transcription Factors / Q000378:metabolism*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D014157:Transcription Factors; D003300:Copper; D008668:Metallothionein