Hemoglobin synthesis during rabbit reticulocyte maturation in vitro

Abstract

A defined medium for the study of rabbit reticulocyte maturation in vitro is described; the use of this medium led to the following observations. 1. 1. During maturation, hemoglobin synthesis itself had no effect on the rate of decay of the reticulocyte's ability to synthesize hemoglobin. 2. 2. Iron deprivation during maturation led to an irreversible loss in the reticulocyte's ability to utilize exogenous iron for hemoglobin synthesis. 3. 3. Addition of hemin to the maturation medium resulted in inhibition of globin synthesis in fresh cells, but stimulation in cells which had been incubated for 20 h. 4. 4. Comparison of whole cell and cell-free protein synthesizing rates of fresh cells and cells incubated for 20 h showed a much greater decline in activity of the whole cells than the cell-free systems derived from them. The conclusion drawn from these observations is that heme synthetic capacity declines more rapidly than globin synthetic capacity during maturation in vitro. This suggests that the duration of heme synthetic capacity may be a quantitatively controlling feature in the development of erythroid cells.