Friend erythroleukemia cells, originally derived from DBA/2 mice, differentiate when cultured with inducing agents. Studies of the different effects of inducing agents on clone 745 have revealed that both dimethyl sulfoxide (DMSO) and hemin produce benzidine-positive cells. Butyric acid produced mature but benzidine-negative cells in this clone. All agents induced globin synthesis above the 0.1% of protein synthesis found in uninduced cells. DMSO induction stimulated globin synthesis 9%, hemin 2%, and butyric acid 3%. Total beta/alpha ratios were approximately unity with all agents. Although the inducing agents all stimulated total globin synthesis in Friend cells, the relative rates of synthesis of the two mouse beta chains were affected differently by the various agents. Hemin markedly increased the proportion of beta minor. For example, DBA/2 mouse reticulocytes synthesized 20% beta minor and 80% beta major. DMSO induction of clone 745 caused 20%-33% synthesis of beta minor. In contrast, hemin increased the proportion of beta minor to 64%-69%. Thus the Friend erythroleukemia cell system provides an in vitro approach to the study of the regulation of globin-chain switching.

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