title: Studies on the influence of nitrite on methemoglobin formation in Amazonian fishes.
abstract: Twenty one species of fishes, collected from the Rio Solimões and a tributary lake in the Amazon Basin near Manaus, showed a wide range of methemoglobin formation 1 hr after a dose of 30 mg/kg of sodium nitrite i.p. Methemoglobin formation in two experimental fishes, Brycon cf. melanopterum and Semaprochilodus insignis, maintained in tanks in our INPA laboratory, was studied in detail. Both fishes survived a dose of 10 mg/kg of nitrite i.p. but usually died within 3 hr of a dose of 30 mg/kg with levels of blood methemoglobin in excess of 80%. Methemoglobin produced in vitro by addition of nitrite to fresh blood was slowly reduced back to hemoglobin over a period of several hours at room temperature. Hemoglobin in hemolysates was auto-oxidized to methemoglobin at pH 6.1 and below but not at 6.9 and above.
mesh_terms: D000818:Animals; D001938:Brazil; D005399:Fishes / Q000097:blood*; D008706:Methemoglobin / Q000378:metabolism*; D009573:Nitrites / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects
chemical_list: D009573:Nitrites; D008706:Methemoglobin; D010100:Oxygen