OBJECTIVES: Bisphenol A (BPA) is a typical endocrine disrupter. We investigated the mechanisms of rapid Ca(2+) signaling induced by a low dose BPA application in cultured hippocampal neurons.
MATERIALS AND METHODS: The primary culture of hippocampal neurons were prepared from postnatal 3 to 5-day-old rats. Cells were loaded with Calcium Green-1 fluorophore. Ca(2+) imaging and analysis were performed by Argus system.
RESULTS: The application of BPA at 10-100 nM induced a transient increase in the intracellular Ca(2+) of N-methyl-D-aspartate (NMDA)-responsive neurons. The Ca(2+) transient occurred within 30 sec after the BPA application. The proportion of BPA-responsive neurons was 9.6 % and 8.5 % of the total NMDA-responsive neurons, respectively, upon 10 nM and 100 nM BPA application. The pre-treatment of neurons with Ca(2+) channel blockers, thapsigargin and nifedipine, considerably decreased the proportion of BPA-responsive neurons to 0.7 % and 3.7%, respectively. The treatment of neurons with an antagonist of estrogen receptor, ICI 182,780, also significantly decreased the proportion of BPA-responsive neurons down to 1.1 %.
CONCLUSION: These results suggest that a low dose BPA application rapidly drives the Ca(2+) signaling system via activation of non-genomic pathway including estrogen receptors.