Satellite versus total DNA replication in relation to endopolyploidy of decidual cells in the mouse

In rodents, decidualization produces large endopolyploid cells. Amongst the various endocycles which have been demonstrated in animals and plants, different modes of DNA replication have been characterized: either total reproduction of all DNA types, or else, underreplication or amplified synthesis affecting specific parts of the genome. A double labelling method was used to determine to which of these categories the case of decidual cells belongs. A mixture of purified DNA from hormonally-stimulated control endometrium labelled by ³H-thymidine and from decidua labelled by ¹⁴C-thymidine was ultra-centrifuged to equilibrium in a Cs₂ SO₄-Ag gradient. Optical density at 260 nm and ¹⁴C/³H ratio were evaluated in serial fractions along the gradient. Since the¹⁴C/³H ratio did not significantly vary along the gradient, it may be concluded that in the case of decidual cells, endopolyploidy corresponds to uniform replication of all nuclear DNA.