Congenital Methemoglobinemia with a Deficiency of Cytochrome B5

Abstract

IT is generally accepted that red cells possess enzymatic reducing mechanisms that maintain hemoglobin in its active state.1 , 2 It is also well established that the reduction is dependent on the regeneration of reduced pyridine nucleotides.3 4 5 Treating red cells with nitrite and incubating them with glucose, lactate, or other substrates that allow the production of reduced pyridine nucleotides promotes methemoglobin reduction.1 , 2 , 6 , 7 Under normal conditions, NADH (reduced nicotinamide adenine dinucleotide) accounts for most of the methemoglobin-reducing capacity of the erythrocyte.2 , 8 9 10 11 An NADH dehydrogenase — variously named methemoglobin reductase or cytochrome b5 reductase — has been proved to be a component of the . . .