Ca2+ oscillations stimulate an ATP increase during fertilization of mouse eggs.
Mammalian eggs and embryos rely upon mitochondrial ATP production to survive and proceed through preimplantation development. Ca(2+) oscillations at fertilization have been shown to cause a reduction of mitochondrial NAD+ and flavoproteins, suggesting they might also cause changes in cytosolic ATP levels. Here, we have monitored intracellular Ca(2+) and ATP levels in fertilizing mouse eggs by imaging the fluorescence of a Ca(2+) dye and luminescence of firefly luciferase. At fertilization an initial increase in ATP levels occurs with the first Ca(2+) transient, with a second increase occurring about 1 h later. The increase in cytosolic ATP was estimated to be from a prefertilization concentration of 1.9 mM to a peak value of 3 mM. ATP levels returned to prefertilization values as the Ca(2+) oscillations terminated. An increase in ATP also occurred with other stimuli that increase Ca(2+) and it was blocked when Ca(2+) oscillations were inhibited by BAPTA injection. Additionally, an ATP increase was not seen when eggs were activated by cycloheximide, which does not cause a Ca(2+) increase. These data suggest that mammalian fertilization is associated with a sudden but transient increase in cytosolic ATP and that Ca(2+) oscillations are both necessary and sufficient to cause this increase in ATP levels.
Campbell
Karen
K
Department of Obstetrics and Gynaecology, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
Swann
Karl
K
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D005260:Female; D005307:Fertilization in Vitro; D008163:Luminescent Measurements; D008540:Meiosis; D051379:Mice; D008856:Microscopy, Fluorescence; D010063:Ovum / Q000378:metabolism*
D000255:Adenosine Triphosphate; D002118:Calcium