phosphoricacidformedisreducedbytheadditionof1-amino2napthol~4-sulphonicacid(ANSA)reagenttoproducethebluecolor.Theactivityofthebluecolorwasreadat680nmagainstreagentblankusingaU.V.Spectrophotometer.Suitablestandardswererunthrougheachbatchofassays.Theenzymeactivitywasexpressedintermsofpgofinorganicphosphorusformedhr'1mg'1protein.

Aftereffluentexposure,thecontrolandeffluentexposedfishtissueswereremovedandplacedinabeakercontainingice-coldSEIbuffer(300mMsucrose,200mMNa2EDTA,50mMimidazole,pH7.23)foranalysisofNa+-K+ATPaseactivity.ThetissueswereimmediatelyfrozeninliquidN2andstoredat-80°Cuntilanalyzed. Thespecificactivitiesofsodium,potassium,magnesiumandcalciumdependentATPaseswereassayedaccordingtothemethodsdescribedbyWatsonandBeamish(1980)and Boeseetal.(1982).AdenosinetriphosphatasecatalysestheconversionofATPandADP.Duringthisconversion,onemolecule ofphosphorusisliberated.ATPaseAdenosinetriphosphate^...^Adenosinediphosphate+PTheinorganicphosphorusliberatedwasassayedaccordingtothemethodofFiskeandSubbarow(1925).Inthismethodtheproteinisprecipitatedwithtrichloroaceticacid.Theproteinfreefiltrateistreatedwithaceticacidmolybdatesolutionandthe