Role of calmodulin in blastocyst formation in the mouse

Abstract

Summary. Preimplantation mouse embryos were recovered by flushing the oviducts on Day 3 at 09:30\p=n-\10:00h, 15:30\p=n-\16:00h and 21:30\p=n-\22:00h: When placed in culture for 48 h, 79% of the 4\p=n-\8cell embryos recovered at 09:30\p=n-\10:00h developed into blastocysts, but a large number of these embryos failed to form blastocysts when exposed to trifluoperazine, a calmodulin antagonist, at 0\m=.\5or 0\m=.\6 \g=m\m in culture. About 45% of the embryos recovered at 15:30\p=n-\16:00h were compacted and blastocyst formation was again markedly depressed in the presence of the drug. Advanced compacted embryos recovered at 21:30\p=n-\22:00 h showed normal development into blastocysts in the presence of 0\m=.\6\g=m\m-trifluoperazine. Trifluoperazine sulphoxide (the inactive form of trifluoperazine) at 0\m=.\6or 1\m=.\2 \g=m\m concentration had no effect on blastocyst formation of uncompacted embryos recovered at 09:30\p=n-\10:00h. These embryos and those recovered at 21:30\p=n-\22:00 h and developed into blastocysts in the presence of trifluoperazine were transferred to Day-4 pseudopregnant mice and healthy young were born. When exposed to calcium-free medium or medium containing trifluoperazine all compacted embryos recovered at 18:30 h became decompacted; development to the blastocyst stage was normal in medium alone but reduced when trifluoperazine was added. Compacted embryos recovered at 23:00 h showed 100% decompaction in the calcium-free medium but completely failed to decompact in the presence of 0\m=.\6 \g=m\m-trifluoperazine. We suggest that extracellular calcium is essential for the continuance of compaction, while intracellular calcium is required only during the initial phase of this process.

Nitric Oxide as a Regulator of Embryonic Development

“…The endothelial isoform of NOS is a constitutively produced calcium-calmodulin-dependent enzyme and was chosen because embryos from each day of early pregnancy produced NO. In addition, other factors such as the requirement of calmodulin for compaction of morula, and increased capillary permeability at the site of implantation, indicated that this may be one form of NOS present in embryos [12]. The inducible isoform of NOS was chosen because its production in macrophages and other cell types is induced, and we determined that after exposure to E 2 the production of NO increased.…”

The preimplantation mouse embryo is a target for cannabinoid ligand-receptor signaling.

“…These two second messengers, involved in important signal transduction pathways, are implicated in cell proliferation, differentiation, and gene expression. In this respect, cAMP has been implicated in zygotic gene activation and blastocyst expansion (32,33), while intracellular Ca2+ plays an important role in the cell polarity and embryonic compaction for morula to blastocyst transformation (34,35).…”

3H‐uridine incorporation in early porcine embryos

“…In mouse embryos, however, RNA synthesis remained low until the four-cell stage and increased 3.4fold between the four-cell and the morula stages and then declined in blastocyst stages (Clegg and Piko, 1977). This sharp rise in genomic activity coincides with the differentiation into inner cell mass and trophectoderm beginning at the eight-cell stage (Pakrasi and Dey, 1984) and is accompanied by changes in protein synthesis and energy metabolism (Ellem and Gwatkin, 1968;Clegg and Piko, 1977;Wales, 1986). At the same time, the number of ribosomes increases (Piko and Clegg, 1982) and cell content of maternal mRNA templates decreases (Adamson and Gardner, 1979).…”