Ali Louei Monfared, Sahar Hamoon Naward, Zahra Bakhteyari, Hajar Azizian and Sara Rahimi
Formaldehyde (FA) is a major source of environmental pollution. FA has been wide applications in the various industries, hospitals and research centers. The aim of present study was to characterize the potential toxicity of formaldehyde of the lymphatic organs and white blood cell count in the rainbow trout after one month exposure.80 O. mykiss were randomly divided into four groups (n=20). Control group was kept in water without any add-on material, while experimental groups were exposed to concentration of 25, 50 and 100 mg/L of FA solution, respectively, for a month. At the end of the administration period, heparinzed blood samples were drawn by cardiac puncture and total white blood cells were counted. Tissue specimens were taken for histological evaluation and prepared sections were stained with Hematoxylin–Eosin (H&E). In the fish treated with formaldehyde; there was a significant reduction in the number of white blood cells count. The histological structure of the spleen of fish treated with formaldehyde revealed histological changes include: increasing in the thickness of the capsule, significant reduction in the lymphoid cell population and increasing in the number of macrophages as well as megakaryocytes in the spleen tissue when compared with controls. In addition, in the experimental groups necrosis and vacuolization of the skin cells in the different layers, impaired regulation of cell keratinocytes and cell dysplasia was seen in the basal layer of the skin. According to these results formaldehyde should be considered as an environmental hazard to fish especially immunosuppressive threaten and its releasing to water supplies would be prevented.
