| Summary: | The effects of hyperosmotic and husbandry related stress on Atlantic salmon (Salmo salar) and the mechanisms employed in response were investigated. To assess the role of taurine and betaine transport proteins in contending with hyperosmotic stress, a cDNA encoding the salmon taurine transporter was cloned. Exposure of various isolated tissues to hyperosmotic stress led to a 2 to 5 fold increase in taurine transporter mRNA. The transfer of juvenile salmon to seawater in October elicited a similar response. Supplementation of culture media with taurine failed to reduce mortality or alleviate a hyperosmotic induced decrease in protein synthesis in isolated tissues. Supplementation of the diet with taurine reduced accumulation of the transporter transcript in salmon smolts, but not in parr. The salmon betaine transporter gene was not found. These investigations suggest a role for taurine in hyperosmotic adaptation in Atlantic salmon and the absence of the betaine transporter. Experiments were performed to isolate and characterize the hsp90 transcript in salmon. A cDNA encoding salmon hsp90 was cloned and transcript was found to be upregulated in gill but not kidney tissue exposed to hyperosmotic conditions in vitro and in vivo. Hsp90 mRNA was upregulated in both gill and kidney tissue subjected to thermal stress in vitro and in vivo. Hsp90 protein increased with thermal stress, but not osmotic stress. The results suggest that accumulation of hsp90 mRNA due to osmotic stress is unrelated to protein denaturation and that synthesis of hsp90 is regulated at both transcription and translation. Studies were conducted to determine whether heat shock protein mRNA might be affected by common forms of hatchery stress in salmon. Hsp70 and 90 mRNA levels increased three-fold and two-fold above control levels following 15 min heat stress, but hsp30 mRNA levels increased two-fold only after 30 min exposure. Most notably, hsp mRNA was not upregulated in response to the different hatchery stresses examined. The findings suggest that hsps 30, 70 and 90 are not sensitive indicators of hatchery stress in Atlantic salmon.
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