title: Hematological responses of the Neotropical teleost matrinxã (Brycon cephalus) to environmental nitrite.
abstract: Environmental increase in nitrite impairs the function of several aquatic species, including fishes. Nitrite reacts with hemoglobin yielding the non-functional methemoglobin (metHb), and many physiological disturbances can arise. The physiological mechanisms to cope with nitrite are still unclear in fish. Hematological parameters, the role of NADH-methemoglobin reductase system and the electrolytic balance were studied in the freshwater teleost Brycon cephalus (matrinxã) exposed to 0.2, 0.4 and 0.6 mg/L of nitrite N-NO(2) for 24 and 96 h. Hematocrit, total hemoglobin and the red blood cell (RBC) number decreased. Methemoglobin content increased from 1% to 69% for 24 h of exposure and drastically from 5-6% to 90% for 96 h. The activity of NADH-methemoglobin reductase system displayed a tendency of increase in response to nitrite concentration or time of exposure. In the plasma, nitrite was accumulated to values 30-fold higher than the environmental concentration. The plasma K(+) concentration increased only in fish exposed to NO(2) for 24 h. No changes in plasma protein and Na(+) were observed during nitrite exposure but Cl-presented a punctual increase at 0.2 mg/L N-NO(2)-96 h. The hematological data suggest that nitrite caused functional and hemolytic anemia. Furthermore, the electrolytic balance was relatively undisturbed, and the nitrite clearance in matrinxã is likely depending on other factors than NADH-methemoglobin reductase system.
authors.affiliation: Departament of Genetics and Evolution, Federal University of São Carlos, Rod Washington Luís, km 235, São Carlos, SP CEP 13565-905, Brazil.
authors.forename: Ive M
authors.initials: IM
authors.lastname: Avilez
authors.forename: Alexandre E
authors.initials: AE
authors.lastname: Altran
authors.forename: Lúcia H
authors.initials: LH
authors.lastname: Aguiar
authors.forename: Gilberto
authors.initials: G
authors.lastname: Moraes
mesh_terms: D000818:Animals; D002712:Chlorides / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004906:Erythrocyte Count; D004909:Erythrocyte Indices; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D005618:Fresh Water; D006400:Hematocrit; D008706:Methemoglobin / Q000187:drug effects* / Q000378:metabolism; D009243:NAD / Q000097:blood; D009249:NADP / Q000097:blood; D009573:Nitrites / Q000097:blood; D010783:Photometry; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D012977:Sodium Nitrite / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors; D014329:Tropical Climate
chemical_list: D002712:Chlorides; D009573:Nitrites; D009243:NAD; D009249:NADP; D008706:Methemoglobin; D012964:Sodium; D012977:Sodium Nitrite; D011188:Potassium