Effect of phosphate on the second cleavage division of the rat embryo.
Development of the rat embryo is arrested at the 2-cell stage in vitro in the presence of inorganic phosphate (Pi). Rat embryos were affected by exposure to 1.19 mM KH2PO4 in modified hamster embryo culture medium-1 at the late 2-cell stage only. When exposure durations were 6 h, embryos whose exposure timings were prior to cleavage had a reduced rate of development to the blastocyst stage (2-8%) when compared with embryos with no exposure to Pi (97%, P < 0.05). When exposure durations were 18 h, all embryos were arrested at the 2- to 4-cell stage. These timings would correspond to the G2 to M phase of the second cell cycle. Maturation-promoting factor (MPF), which is regulated by a phosphorylation cascade, controls cell division, and its kinase activity is necessary in order for the cell to enter the M phase. However, the histone H1 kinase activity levels and the patterns of the state of phosphorylation of cdc2 were the same in blocked and non-blocked embryos. Because MPF was active in blocked embryos, the developmental block in rat 2-cell embryos caused by phosphate was not due to MPF activity or its phosphorylation cascade.
Matsumoto
H
H
Department of Animal Sciences, Tohoku University, Sendai, Japan.
Sugawara
S
S
D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002970:Cleavage Stage, Ovum / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D006224:Cricetinae; D005314:Embryonic and Fetal Development / Q000187:drug effects / Q000502:physiology; D005260:Female; D016195:G2 Phase / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D016200:Maturation-Promoting Factor / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D010710:Phosphates / Q000494:pharmacology*; D010766:Phosphorylation; D011247:Pregnancy; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D010710:Phosphates; D011494:Protein Kinases; C102333:histone H1 kinase; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor