 although fish in natural populations may carry high body burdens of both organic and inorganic mercury , the effects of this divalent metal on such lower vertebrates is poorly understood . in this report , inorganic mercury in the form of mercuric chloride ( hgcl2 ) 
 is shown to produce both high - dose inhibition and low - dose activation of leukocytes in a marine teleost fish , sciaenops ocellatus . 
 concentrations of inorganic mercury > or = 10 microm suppressed dna synthesis and induced rapid influx of radiolabeled calcium , as well as tyrosine phosphorylation of numerous cellular proteins . lower concentrations ( 0.1 - 1 microm ) of hgcl2 that activated cell growth also induced a slow sustained rise in intracellular calcium in cells loaded with the calcium indicator dye fura-2 , but did not produce detectable tyrosine phosphorylation of leukocyte proteins . 
 these studies support the possibility that subtoxic doses of hgcl2 may inappropriately activate teleost leukocytes , potentially altering the processes that regulate the magnitude and specificity of the fish immune response to environmental pathogens.imagesfigure 1.figure 2.figure 3.figure 4.figure 5.figure 6.figure 7 . 
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