Stage-specific response of preimplantation mouse embryos to W-7, a calmodulin antagonist.
Involvement of calmodulin-dependent processes in preimplantation development of mouse embryos was studied with the use of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a specific antagonist of calmodulin. At 25 microM, W-7 interfered with compaction of eight-cell embryos, caused decompaction of compacted eight-cell embryos, inhibited cavitation of late morulae, and caused collapse and degeneration of blastocysts. These effects of W-7 appear to be due to specific inhibition of calmodulin-dependent processes, because W-5, a less active analogue of W-7, was less effective in interfering with development; at 25 microM, W-5 had only a slight effect on compaction and had no effect on blastocyst formation, maintenance of blastocoels, or post-blastocyst development. In addition to the developmental effects just described, W-7 inhibited cell proliferation in four-cell embryos and reduced cell numbers of morulae after treatment at the two- to eight-cell stages. There was a marked increase in embryos' sensitivity to W-7 at the late morula stage, and the sensitivity increased further as embryos developed into blastocysts; the effects of W-7 were largely reversible after treatment at the two-cell through the compacted eight-cell stages, but not after treatment at the late morula or blastocyst stage. At the blastocyst stage, inner cell mass cells appeared to be slightly more resistant to W-7 than trophectoderm cells. This differential sensitivity became more pronounced at the late blastocyst stage: after 3.5-4-h exposure of late blastocysts to 25 microM W-7, all trophectoderm cells degenerated but most of the inner cell masses survived. From these results it appears that calmodulin-dependent processes are involved in development of mouse embryos at all of the preimplantation stages examined.
Yamaura
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Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143.
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D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002455:Cell Division / Q000187:drug effects; D003470:Culture Media; D051379:Mice; D013449:Sulfonamides / Q000494:pharmacology*; D013997:Time Factors; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects
D002147:Calmodulin; D003470:Culture Media; D013449:Sulfonamides; C017967:W 7