抄録
OBJECTIVE: Endocrine disrupters (EDs) showing estrogen-like actions are believed to interfere with the function of reproductive systems. Although their effects on spermatozoa are extensively studied, few reports are available for oocytes. The present work therefore aims to elucidate the effects of estrogen itself and bisphenol-A (BPA) on mouse oocytes. METHODS: Immature germinal vesicle (GV) oocytes, obtained from the ovaries of adult mice (ICR strain), were loaded with Fura-2, and their dynamic changes in [Ca2+]i were monitored using Argus 50 and Argus HiSCA image analyzers (Hamamatsu Photonics). RESULTS: The majority of oocytes exhibited spontaneous Ca2+ oscillations at regular intervals. Also, oocytes in ovarian slices with a thickness of approximately 100 mm showed similar Ca2+ oscillations. Application of 17β-estradiol (E2), the most potent natural estrogen, to oocytes by perfusion suppressed the Ca2+ oscillations in a dose-dependent manner (1 nM - 1 μM), i.e., 1) the regular pattern of Ca2+ oscillations was perturbed, 2) the interval between Ca2+ rises was prolonged with time, and 3) the amplitude of the Ca2+ elevation gradually decreased and was finally suppressed. Application of 10 mM BPA significantly disrupted the pattern of Ca2+ oscillations. DISCUSSION: The results suggest that 1) spontaneous Ca2+ oscillations in ovarian oocytes are controlled by estrogen, in preparation for fertilization, and 2) BPA affects oocytes by interfering with this control mechanism. [Jpn J Physiol 54 Suppl:S224 (2004)]
