Poly I:C-induced Mx responses in Atlantic salmon parr, post-smolts and growers.
Intraperitoneal injection of 500 microg poly I:C/fish into Atlantic salmon parr in freshwater and post-smolts and growers in seawater (all at 11 degrees C) induced enhanced expression of Mx mRNA in liver tissue 24 h post-injection. The level of Mx transcripts peaked at day 3 (Mx:beta-actin ratio of about 0.8) and the response disappeared by day 7. In post-smolts, mortalities occurred up to day 14 post-injection, which was dose-dependent. Histological examination of tissues revealed severe pathological changes in the liver of poly I:C injected post-smolts resulting from apoptosis and necrosis of hepatocytes. All other organs appeared histologically normal. Levels of Mx mRNA expression on day 3 post-injection were similar for fish with normal and pathological livers. In untreated or control fish injected with PBS, low levels of Mx transcripts (Mx:beta-actin ratio about 0.1) were sometimes detectable in parr but not in growers. Constitutive Mx expression was variable in post-smolts. Some populations had no detectable transcripts while in others moderate ratios (about 0.3) were detectable over a 3-week period of sampling. Poly I:C administered to parr by bath or orally did not induce upregulation of Mx expression.
Marine Laboratory, Victoria Road, Aberdeen AB11 9DB, Scotland, UK.
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K
Lockhart
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TJ
Bowden
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Ellis
D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D017931:DNA Primers; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water; D019204:GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects*; D020287:In Situ Nick-End Labeling; D008099:Liver / Q000378:metabolism / Q000473:pathology; D064547:Myxovirus Resistance Proteins; D011070:Poly I-C / Q000276:immunology / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020317:Salmo salar / Q000276:immunology*; D012623:Seawater; D013997:Time Factors
D017931:DNA Primers; D064547:Myxovirus Resistance Proteins; D012333:RNA, Messenger; D019204:GTP-Binding Proteins; D011070:Poly I-C