Induced thermotolerance and tissue Hsc70 in juvenile coho salmon, Oncorhynchus kisutch

We examined Hsc70 in gill, liver and caudal fin from coho salmon (Oncorhynchus kisutch) before (ambient, similar to 12 degrees C) and after a sublethal heat shock of 25 degrees C for 1 h. Increased levels were observed for at least 48 h in all three tissues. Attempts to demonstrate isoforms of this heat-shock protein were not successful using four different antibodies. However, one of these antibodies recognized isoforms in brine shrimp and oysters, two organisms in which the heat-shock response has been well characterized. Extracts of those organisms and coho salmon tissues were run on the same gels and evaluated on the same Western blots, at the same time. We believe that our results provide a reliable account of Hsc70 in these fish under these conditions. Limited experiments showed that induced thermotolerance was achieved in these coho salmon, lasting for about 1 week after the sublethal heat shock. These data suggest that increased levels of Hsc70 are correlated with induced thermotolerance in these fish.