Fluorescent cytoplasm and Heinz bodies of hemoglobin Köln erythrocytes: evidence for intracellular heme catabolism.

Hb Köln, one of the common mutant hemoglobins responsible for unstable hemoglobin disease, was found to be degraded to a fluorescent yellow pigment (FYP) in circulating erythrocytes. FYP is responsible for a strong green fluorescence observed in the cytoplasm and is particularly abundant in the Heinz bodies of Köln RBC. Front face fluorometry and fluorescence microscopy showed that Heinz bodies emit 10% to 20% of the fluorescence of RBCs. Hb-free FYP was obtained by means of a cellulose column separation of the cytoplasm or from a precipitate formed during the incubation of Köln RBC cytoplasm at 50 degrees C. The absorption and emission spectra of FYP are consistent with those of dipyrroles.