Blastocyst Cavitation is Accelerated by Ethanol- or Ionophore-Induced Elevation of Intracellular Calcium1

To extend our previous finding that ethanol stimulates murine preimplantation development, we focused in the current study on the cavitation and expansion of the blastocyst. Ethanol stimulation of blastocyst cavitation and expansion was optimal at a concentration of 0.1% and required only a 5-min exposure. Because intracellular levels of calcium were transiently increased in the ethanol-exposed embryos, we determined the effect of directly increasing calcium on the rates of blastocyst cavitation and expansion. Treatment with the calcium ionophore, A23187, altered development much as did ethanol, indicating that ethanol may stimulate preimplantation development by increasing the intracellular calcium concentration. The relationship between intracellular calcium levels and blastocoel volume suggests that morphogenetic events during preimplantation development, particularly cavitation and blastocyst formation, may be regulated through modulation of intracellular calcium levels.