 three species of chesapeake bay fish were collected , and endogenous levels of metal binding protein ( mbp ) were determined . 
 in addition , the induction of metal - binding proteins by cadmium was studied . 
 livers from freshly caught fish were extracted and chromatographed on sephadex g-75 to resolve mbp in the 5 to 20 kdalton range . 
 all species studied exhibit measurable but varied levels of endogenous mbps in the molecular weight range investigated , mostly as a copper protein complex . upon induction with cadmium , 
 the total mbp content increased in both catfish ( ictalurus punctatus ) and striped bass ( morone saxatilis ) , with significant amounts of cadmium bound to the protein . in white perch ( morone americana ) , induction of mbps with cadmium could not be demonstrated due to the large amount of constitutive cu - bp present , although significant quantities of cadmium were bound to mbp . 
 electrophoresis in polyacrylamide gel was used to further identify these mbps . 
 electrochemical analysis of the mbps by polarography indicated that the wave properties of the fish mbps resemble that of rat metallothionein . in conclusion , these studies indicate that : mbps are present in estuarine fish from the chesapeake bay ; concentrations of mbps and their inducibility by exogenous cadmium vary with species , and fish mbps may be related to mammalian metallothionein.imagesfigure 7 . 
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