Fast action of estrogen on intracellular calcium in dormant mouse blastocyst and its possible mechanism

ObjectiveTo study the fast action of estrogen on intracellular calcium of dormant mouse blastocysts and the possible mechanism.DesignControlled, prospective study.SettingAcademic research unit.Animal(s)Forty adult Kun-ming mice.Intervention(s)A laser scanning confocal microscope was used to detect the dynamic change of intracellular calcium labeled by Fluo-3/AM, a fluorescent probe of calcium, which was caused by 17-beta-estradiol (17β-E2) in dormant mouse blastocysts. A fluorescent microscope was used to check out the alteration of [Ca2+]i induced by E2-BSA, a large molecule of estrogen coupling with bovine serum albumin; by 17β-E2 with Ca2+-free M2 medium; by 17β-E2 with tamoxifen, a blocking agent of traditional estrogen receptor (ER); and by 17β-E2 with U73122, a specific inhibitor of phospholipase C. Immunocytochemistry was used to detect the change of intracellular phosphorylated phospholipase C (p-PLC) induced by 17β-E2.Main Outcome Measure(s)Intracellular calcium and intracellular p-PLC in dormant mouse blastocysts.Result(s)Both 17β-E2 and E2-BSA could increase the intracellular calcium concentration ([Ca2+]i) of blastocysts rapidly, and this increase of [Ca2+]i was independent of either estrogen getting into the cells or the extracellular calcium in the incubation medium. However, this action was possibly blocked by a specific inhibitor of phospholipase C but not by the traditional blocking agent of ER. Moreover, the intracellular p-PLC increased after estrogen acting on blastocysts.Conclusion(s)Estrogen may induce the increase of intracellular calcium in dormant mouse blastocysts by its action on the composition of the cell membrane to cause the release of Ca2+ from the endoplasmic reticulum through the transmembrane signal transduction mediated by PLC.