Accumulation of RNA in blastocysts during embryonic diapause and the periimplantation period in the western spotted skunk

The in vivo incorporation of 3H-uridine into RNA was studied in delayed implanting and activated blastocysts obtained from 33 western spotted skunks. 3H-uridine was incorporated into RNA by all blastocysts; however, significantly more label was incorporated as blastocyst diameter increased. Activated blastocysts with diameters of 1.6 mm or greater on average incorporated 65 times more 3H-precursor in 5 hr than diapausing blastocysts with diameters of 1.1 mm or less. Polyadenylated RNA was likewise synthesized by delayed implanting and activated skunk blastocysts; however, the proportion of polyadenylated RNA synthesized by the former was greater than in the latter (43.9% vs. 27.5%). Our data suggest that the transition from embryonic diapause to fully activated blastocysts first occurs gradually for several days before entering a 1-2-day period of rapid development characterized by an abrupt increase in RNA accumulation.