Progesterone induced diminished incorporation of exogenous 14C-amino acids in diapausing mouse blastocysts.

Under identical in vitro labeling conditions, significantly lower amounts of radioactivity were found a) in proteins of early diapausing blastocysts (days 7-9 p.c.) vs normal, late blastocysts (day 5 p.c.) and b) in proteins of days 19-23 p.c. diapausing blastocysts from ovariectomized mothers treated with progesterone vs similar embryos from untreated mothers. Thus, progesterone, which maintains the viability of embryos during prolonged diapause, causes diminished utilization of exogenous amino acids for protein synthesis in these embryos.