The effects of activators of protein kinase C (PKC) on the development of mouse late morulae were examined by morphological techniques. Late morulae were cultured with low levels of the PKC activators phorbol 12-myristate 13-acetate (PMA
0.01-1 nM) and 1-oleoyl 2-acetyl-sn-glecerol (OAG
0.1–10 μM) for 24 h, their blastulation ratios were determined and morphological changes in intracellular distribution of actin filaments were examined. PMA treatment induced the decompaction of morulae and delayed blastocoel formation. OAG treatment induced delayed embryonic development. Both PMA and OAG treatment induced reorganization of actin filaments in late morulae. It is assumed that PKC activation induces reversible arrest of embryonic morphogenesis in mouse late morulae. © 1997, JAPANESE SOCIETY OF OVA RESEARCH. All rights reserved.