Calcium oscillations and protein synthesis inhibition synergistically activate mouse oocytes.
We have examined the ability of the two parthenogenetic agents, strontium (Sr2+) and cycloheximide, to activate mouse oocytes. We demonstrate that Sr2+ and cycloheximide act synergistically to promote parthenogenetic activation up to the pronuclear stage in oocytes collected immediately after ovulation. These two agents appeared to act independently, since incubation in Sr2+ media triggered a series of intracellular Ca2+ rises without affecting protein synthesis and cycloheximide inhibited protein synthesis without causing any intracellular Ca2+ changes. In addition, cycloheximide did not alter the pattern of Ca2+ oscillations induced by Sr2+. In contrast, we show that another commonly used parthenogenetic activation treatment, the Ca2+ ionophore A23187, has dual effects. Exposure of oocytes to the Ca2+ ionophore, A 23187, in Ca(2+)- and Mg(2+)-free medium leads to the activation of young oocytes. However, as well as generating a Ca2+ increase, the treatment of mouse oocytes with A23187 and Ca(2+)- and Mg(2+)-free media led to a marked inhibition of protein synthesis. Our data show that parthenogenetic agents may have two important loci for activating mammalian oocytes and that the combined effect on Ca2+ release and protein synthesis is most effective.
Bos-Mikich
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A
MRC Experimental Embryology and Teratology Unit, St. George's Hospital Medical School, London, UK.
Swann
K
K
Whittingham
D G
DG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology*; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D014176:Protein Biosynthesis; D013324:Strontium / Q000494:pharmacology*
D003513:Cycloheximide; D002118:Calcium; D013324:Strontium