| Abstract: | We cultured human adult peripheral and umbilical cord blood mononuclear cells in methylcellulose and measured the synthetic rates of globin chains in individual erythropoietic bursts. Globin chains were labeled with 14C-amino acids in culture, separated by isoelectric focusing in slab gels containing 8 M urea and 3% Nonidet P-40, and quantitated by fluorographic methods. All bursts exhibited G gamma, A gamma, and beta chains in varying ratios. Cumulative frequency distributions of individual bursts differing in the ratios of G gamma/(G gamma + A gamma) and gamma/(gamma + beta) approached normal distributions. These results indicated that perinatal hemoglobin switching and the hemoglobin switching of cultured adult erythropoietic precursors do not involve population changes in the precursors. Further, a positive correlation between gamma/(gamma + beta) and G gamma/(G gamma + A gamma) ratios of individual bursts existed in all of the samples. Switching between gamma and beta chains and switching of G gamma: A gamma ratios may share common regulatory mechanisms. |
