Red cell NADP+ and NADPH in glucose-6-phosphate dehydrogenase deficiency.

Extraction in the presence of sodium hydroxide and cysteine allows estimates of NADPH and total NADP in human red cells without the erroneously high values of NADP+ obtained with earlier methods. An application of this technique to G6PD-deficient cells reveals that most of the nucleotide is in the oxidized form. In contrast, normal red cells have nearly all of the nucleotide in the reudced form. In addition to providing information concerning the intracellular regulation of the hexose monophosphate shunt, these findings support the concept that G6PD deficiency is a product-deficiency disorder.