Incorporation of Labeled Nucleic Acid and Protein Precursors by Diapausing and Nondiapausing Blastocysts1, 2

Abstract

Embryo culture and radioautographic techniques were used to detect incorporation of precursors of DNA, RNA and proteins by blastocysts of mammals with and without a delayed implantation. These experiments reveal the absence of labeled thymine incorporation by diapausing blastocysts from mink, fur seal, and lactating rat, although thymine is incorporated by nondiapausing rabbit and rat blastocysts. There is little or no incorporation of labeled uracil by blastocysts from those animals which have a relatively long and obligate diapause; but significant levels of uracil incorporation are present in the blastocysts from lactating rats, which have a shorter and facultative delay. Conversely, nondiapausing blastocysts of rat and rabbit have high levels of nucleic acid synthesis, as judged by incorporation of the labeled precursors.