Phyto- and endogenous estrogens differently activate intracellular calcium ion mobilization in bovine endometrial cells

Abstract

The main purpose of this study was to check whether phyto- and endogenous estrogens influence calcium ion mobilization [Ca2+]i in bovine endometrial cells and whether this action is connected with biological effects i.e. prostaglandin (PG)F2α production. In our study we used two calcium measurement methods by comparing the microscopic method with widely used quantitative - spectrofluorometric method of [Ca2+] i measurement. We also wanted to confirm whether visualization of calcium ion [Ca2+]i in cells using microscopic method supported by micro image analysis (Micro Image Olympus system) reflects real, qualitative changes in the ion concentration. In both methods a cell-permeable form of fluorescent [Ca2+]i indicator Fura-2 was used. Cultured bovine endometrial epithelial and stromal cells influenced by phorbol-2-myristate-13-acetate (PMA; positive control), estradiol 17-β (E2; endogenous estrogen) and active metabolites of phytoestrogens (environmental estrogens) were used as a model to study PGF2α secretion and [Ca2+]i mobilization in the cells. Equol and para-ethyl-phenol in doses of 10-8-10-6 M increased PGF2α concentration both in epithelial and stromal cells (P<0.05). In both methods, equol and para-ethyl-phenol did not cause intracellular [Ca2+] i mobilization in epithelial and stromal cells (P>0.05). Both methods revealed that only E2 and PMA induced intracellular [Ca 2+]i mobilization in epithelial and stromal cells (P<0.05). The results of both methods were highly correlated (P<0.001; r=0.82 for epithelial cells and r=0.89 for stromal cells). In conclusion, both methods gave approximately the same results and showed that phytoestrogens, in contrast to PMA and E2, did not cause intracellular [Ca 2+]i mobilization in endometrial cells. The obtained results proved that the [Ca2+]i visualization method supported by micro image analysis can produce similar results to the spectrofluorometric method.