title: Growth hormone transgenesis and polyploidy increase metabolic rate, alter the cardiorespiratory response and influence HSP expression in response to acute hypoxia in Atlantic salmon (Salmo salar) yolk-sac alevins.
abstract: Growth hormone (GH)-transgenic Atlantic salmon display accelerated growth rates compared with non-transgenics. GH-transgenic fish also display cardiorespiratory and metabolic modifications that accompany the increased growth rate. An elevated routine metabolic rate has been described for pre- and post-smolt GH-transgenic salmon that also display improvements in oxygen delivery to support the increased aerobic demand. The early ontogenic effects of GH transgenesis on the respiratory and cellular physiology of fish, especially during adverse environmental conditions, and the effect of polyploidy are unclear. Here, we investigated the effects of GH transgenesis and polyploidy on metabolic, heart and ventilation rates and heat shock protein (HSP) levels after exposure to acute hypoxia in post-hatch Atlantic salmon yolk-sac alevins. Metabolic rate decreased with decreasing partial pressures of oxygen in all genotypes. In normoxia, triploid transgenics displayed the highest mass-specific metabolic rates in comparison to diploid transgenics and non-transgenic triploids, which, in contrast, had higher rates than diploid non-transgenics. In hypoxia, we observed a lower mass-specific metabolic rate in diploid non-transgenics compared with all other genotypes. However, no evidence for improved O2 uptake through heart or ventilation rate was found. Heart rate decreased in diploid non-transgenics while ventilation rate decreased in both diploid non-transgenics and triploid transgenics in severe hypoxia. Regardless of genotype or treatment, inducible HSP70 was not expressed in alevins. Following hypoxia, the constitutive isoform of HSP70, HSC70, decreased in transgenics and HSP90 expression decreased in all genotypes. These data suggest that physiological changes through GH transgenesis and polyploidy are manifested during early ontogeny in Atlantic salmon.
authors.affiliation: CSIRO National Food Futures Flagship, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, TAS 7001, Australia elias.polymeropoulos@csiro.au.
authors.forename: Elias T
authors.initials: ET
authors.lastname: Polymeropoulos
authors.affiliation: AquaBounty Farms, Souris, PE, Canada C0A 2B0.
authors.forename: Debbie
authors.initials: D
authors.lastname: Plouffe
authors.affiliation: Department of Biology, Mount Allison University, Sackville, NB, Canada E4L 1G7.
authors.forename: Sacha
authors.initials: S
authors.lastname: LeBlanc
authors.affiliation: CSIRO National Food Futures Flagship, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, TAS 7001, Australia.
authors.forename: Nick G
authors.initials: NG
authors.lastname: Elliott
authors.affiliation: Department of Biology, Mount Allison University, Sackville, NB, Canada E4L 1G7.
authors.forename: Suzie
authors.initials: S
authors.lastname: Currie
authors.affiliation: University of Tasmania, Hobart, TAS 7001, Australia.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Frappell
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D030801:Animals, Genetically Modified; D001481:Basal Metabolism; D004171:Diploidy; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D020317:Salmo salar / Q000235:genetics / Q000502:physiology*; D057885:Triploidy
chemical_list: D006360:Heat-Shock Proteins; D013006:Growth Hormone; D010100:Oxygen
keywords: Growth hormone transgenesis; Heat shock proteins; Hypoxia; Metabolic rate; Oxygen transport; Polyploidy; Salmo salar