Microspectrophotometric determination of nonheme iron in maturing erythroblasts and its relationship to the endocellular hemoglobin formation.

By C. A. SONDHAUS AND Bo THORELL D URING the growth and differentiation of erythroid cells, iron is incorporated and passes from the inorganic state into heme compounds, finally producing the normal hemoglobin complement of the mature red blood cell. It has been suggested’4 that the process presumably involves the chelation of iron by a protoporphyrinogen or reduced protoporphyrin. A heme-forming enzyme in reticubocytes has been described,0 and evidence for the location of the enzymic conversion of protoporphyrin and iron to heme within the mitochondria has been presented by Nishida and Labbe.#{176} Vogel, Richert and SchulmanT proposed that iron itself plays a specific catalytic robe in the sequence of reactions from glycine to protoporphyrin prior to its chelation to form heme. The time course of iron uptake in normal hemopoiesis has been studied radioautographically with Fe09 by Austoni,8 and by Suit, Lajtha, Oliver and Ellis,9 who found uptake to be continuous throughout differentiation, the proerythroblasts showing somewhat higher uptake than the other stages. In recent electron microscope studies, Bessis and Breton-Gorius10” have demonstrated the presence of ferruginous granules in the spleen and bone marrow reticulum cells and also in the young erythrobbasts which frequently cluster around them; in the abnormal states these granules are large and have long been observed in the light microscope as “iron pigments.” The present study represents an attempt to obtain microspectrophotometric evidence of the presence of inorganic or “ferritin” iron in erythroblasts during normal hemopoiesis, and further, to study its quantitative relation to the extent of hemoglobinization in the individual cells at different maturation states.’2 The relatively high absorption-coefficients of both constituents at different regions of the ultraviolet and visible spectrum makes it possible in principle to identify each in the presence of the other within a single cell and to draw some conclusions as to their relative amounts as the red cell maturation proceeds. MATERIAL AND METHODS