Capacity of ringed sideroblasts to synthesize nucleic acids and protein in patients with primary acquired...

Bone marrow cells from two patients with primary acquired sideroblastic anaemia were studied using the technique of electron microscope autoradiography. Whereas a significant proportion of erythroblasts containing small to moderate quantities of intramitochondrial deposits incorporated [3H]thymidine into DNA, the majority of cells containing large quantities of intramitochondrial deposits did not. These results are consistent with the idea that several of the early polychromatic cells with large quantities of deposits become arrested in their progress through the cell cycle. The data also revealed that the accumulation of increasing quantities of iron-containing material within the mitochondria of an erythroblast was frequently (but not invariably) associated with and was possibly responsible for (I) a depression of RNA synthesis and (2) a more marked depression of protein synthesis. A small proportion of the erythroblasts showing a depression of protein synthesis also displayed various non-specific ultrastructural abnormalities indicative of cellular injury such as the presence of intranuclear clefts, nuclear membrane-associated myelin figures and lipid-laden intracytoplasmic vacuoles.