Flow cytometry in the analysis of hematological parameters of tilapias: applications in environmental aquatic toxicology

Blood tissue has been used to assess animal health and the environment in which they live. This tissue is easily acquired and has the ability to respond to various adverse conditions. Several techniques have been employed in the detection of xenobiotic-induced cell damage in blood cells. In general, traditionally used technologies, such as cellular analysis in blood smears, are time-consuming and require great analytical capacity. The present study proposes flow cytometry as a method to detect changes in blood cell populations. Tilapia ( Oreochromis niloticus ) was selected as a model for plotting the profile of fish blood cell populations after exposure to xenobiotics without euthanizing animals or using cell markers. Populations of erythrocytes and lymphocytes were detected only by combining the techniques of FACSAria cell sorting and light microscopy. Systemic deleterious effects were found through blood analysis, such as an increased lymphocyte-rich population at 48 h of exposure followed by a subsequent decrease. Moreover, the time-dependent expression of Nrf2 suggests its participation in increased membrane disruption, indicating it has a central role in erythrocyte lifespan. The present results shed light on the viability of using flow cytometry for blood analysis of living fish.