Studies on the influence of nitrite on methemoglobin formation in Amazonian fishes

Abstract

1. 1. 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. 2. 2. Methemoglobin formation in two experimental fishes, Brycon cf. melanopterum and Semaprochilodus insignis, maintained in tanks in our INPA laboratory, was studied in detail. 3. 3. 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%. 4. 4. 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. 5. 5. Hemoglobin in hemolysates was auto-oxidized to methemoglobin at pH 6.1 and below but not at 6.9 and above. © 1987.