ADENINE AND PYRIDINE-NUCLEOTIDES IN ERYTHROID CELL-DEVELOPMENT

Marrow-bound erythroblasts and circulating reticulocytes were consider ed in this study as two progressive stages of erythroid cell developme nt. The contents of ATP, ADP, AMP, ITP, inosine, hypoxanthine, xanthin e, NAD and NADP were determined in the two cell populations immediatel y after the extraction of the cells from the animal body and after inc ubations in different media. In the former case, the content of ATP, I TP and NAD was found to be markedly decreased in reticulocytes with re spect to erythroblasts. In contrast, the decay of the other compounds was negligible taking into account the change of volume between the tw o cell populations. In the latter case, we found that erythroblasts in cubated in the absence of glucose showed a marked decrease of ATP, ITP and NAD content within the first hour, while NADP was constant. In re ticulocytes incubated under the same conditions only ATP decreased. In the presence of glucose, erythroblasts showed a significant decrease of ATP and ITP, while reticulocytes showed a constant content of all n ucleotides. A moderate but significant decay of ATP content was also s hown in erythroblasts incubated in a complete culture medium. In all c ases, the lost ATP and ITP were almost completely transformed into hyp oxanthine. The results indicate that (a) the content of adenine and py ridine nucleotides is significantly reduced in the transition from mar row-bound erythroblasts to circulating reticulocytes; (b) ATP content is linked to ITP in erythroblasts but not in reticulocytes and (c) ery throblasts are not able to maintain in vitro the same nucleotide conte nt found in vivo, while reticulocytes maintain the energetic charge co nstant only in the presence of glucose.