Autoradiography of 3H-uridine incorporation in the normal early blastocysts of cattle

RNA synthesis in morphologically normal early bovine blastocysts collected 7 days after insemination was investigated using fine-structure autoradiography after 3H-uridine incorporation. The level of autoradiographic labelling is proposed as a criterion for assessing metabolic activity in the individual cells of the blastocyst. There was a detectable difference between the cells of the trophoblast and those of the inner cell mass (higher labelling), indicating a divergence of metabolic patterns according to blastomere differentiation. The occasional absence of nuclear labelling was correlated with cell degeneration. A low nuclear labelling was observed mainly in cells sequestered in the subzonal space or in the blastocoele cavity, respectively. Estimation of RNA synthesis in different blastomeres by fine structure autoradiography opens the way to a better interpretation of the relationship between morphology and metabolism during the development of early cow embryos