Can Copper Sulfate Pre-Treatments Induce Resistance to Ammonia Challenge in Channel Catfish

Heat shock treatments initiate cellular responses that lead to transitory periods of enhanced resistance to high temperatures as well as other water quality stressors, but the potential risks associated with heat treatments limits their application in fish. Our laboratory is evaluating alternative therapeutic approaches that are thought to activate the cellular mechanisms of cross-protection (e.g. molecular chaperones); one such alternative is copper sulfate.  After collecting preliminary data that suggested an increased heat tolerance following copper sulfate treatments, we began a series of experiments to discern if copper sulfate could induce resistance to elevated ammonia concentrations.  The data shown here compare the responses of channel catfish Ictalurus punctatus fingerlings exposed to a two-hour LC50 concentration of unionized ammonia that had been pre-treated with either a heat-shock treatment or a copper sulfate bath.  Copper sulfate bath treatments did not appear to provide the same level of resistance to ammonia as heat-shock treatments.  These data concur with the observation by others that metal ions like copper may be weaker inducers of molecular chaperones such as HSP70 than heat treatments.