Environmental contaminants can interfere with
hormonal regulation in both vertebrates and invertebrates, and these contaminants may disrupt the
endocrine system of human and other organisms. Evidence is growing that contaminants may be partly responsible for the observed increase of disease in marine organisms by adversely affecting their immunity. Fish are commonly used as sentinel organisms in vertebrate
immunotoxicology; however, to date, studies have been undertaken only on a single size group of fish (juvenile/adult) and for
acute exposure. In the present study, Lateolabrax japonicus fingerlings and juveniles were exposed to two sublethal concentrations (200 and 2,000 ng/L) of 17beta-estradiol (E2) for 30 d under laboratory conditions, and alterations in
immune parameters comprising differential
leukocyte count,
respiratory burst,
myeloperoxidase,
immunoglobulin levels, serum
lysozyme, and
bactericidal activity were investigated to establish whether
estrogen produced immunomodulation and to understand the effects of long-term exposure on these
immune parameters in fish fingerlings and juveniles. The results revealed a significant elevation of
respiratory burst activity,
myeloperoxidase,
immunoglobulin levels, and differential
leukocyte counts of the fish exposed to
estrogen compared to the control. The remaining parameters were significantly reduced in the experimental groups when compared to the control. The results indicated that sublethal E(2) exposure induced immunomodulation in both fingerling and juvenile L. japonicus, and the changes caused by
estrogen might affect the function of
immune system in fish.
