Effect of inhibitors of polyamine synthesis on activation of diapausing mouse blastocysts in vitro.

Diapausing mouse blastocysts were cultured in vitro with inhibitors of polyamine synthesis and/or the polyamines, putrescine, spermidine and/or spermine. Attachment of blastocysts to the culture dish, the onset of trophoblastic outgrowth and the extent of outgrowth were retarded by methylornithine (10 mM) or methylglyoxal bis(guanylhydrazone) (50 or 200 microM) and apparently blocked by a combination of these inhibitors. The embryos appeared to make no progress towards activation in the presence of both inhibitors but became active and grew normally when transferred to inhibitor-free medium. The inhibition of growth was also reversed when polyamines (10(-5) M) were supplied in the medium along with the inhibitors (P less than 0.01). These results suggest that polyamine synthesis is required for activation, growth and development of diapausing blastocysts in vitro.