Kaufman M L, Homa S T
Department of Zoology, Arizona State University, Tempe 85287.
J Exp Zool. 1993 Jan 1;265(1):69-76. doi: 10.1002/jez.1402650110.
The role of calcium (Ca++) during spontaneous meiotic maturation of pig oocytes was examined. The hypothesis that elevations of endogenously derived intracellular Ca++ are prerequisite for germinal vesicle breakdown (GVBD) and progression through meiosis was tested. In addition, investigations were carried out to determine whether GVBD and meiotic progression were dependent upon extracellular Ca++ influx. Elevation of endogenously derived Ca++ was inhibited directly by loading cells with BAPTA, a specific Ca++-chelator, or indirectly with neomycin. Extracellular Ca++ influx was prevented by culturing oocytes in Ca(++)-deficient medium, with EGTA, or in the presence of the Ca++ channel blocker verapamil. Pretreatment with BAPTA/AM and subsequent culture in the absence of added exogenous Ca++ resulted in a similar inhibition of GVBD (1 microM BAPTA/AM vs. untreated, P < 0.01). After 4 h following follicular release, oocytes were no longer sensitive to BAPTA/AM treatment. Neomycin also significantly inhibited GVBD (0.5 mM neomycin vs. untreated, P < 0.05) as well as meiotic progression past metaphase I (0.25 mM neomycin vs. untreated, P < 0.05). The incidence of GVBD was not significantly affected when oocytes were simply cultured in Ca++ deficient medium or when cultured in the presence of EGTA or verapamil. However, progression of meiosis past GVBD to metaphase II was suppressed by reducing levels of Ca++ in the culture medium (0.68 mM Ca++ vs. 1.7 mM Ca++, P < 0.05) and by treatment with verapamil (0.25 mM verapamil vs. untreated, P < 0.05). Meiotic progression was completely blocked at metaphase I in the presence of 0.85 mM EGTA.(ABSTRACT TRUNCATED AT 250 WORDS)
研究了钙（Ca++）在猪卵母细胞自发减数分裂成熟过程中的作用。检验了内源性细胞内Ca++升高是生发泡破裂（GVBD）和减数分裂进程的先决条件这一假说。此外，还进行了研究以确定GVBD和减数分裂进程是否依赖于细胞外Ca++内流。通过用特定的Ca++螯合剂BAPTA加载细胞直接抑制内源性Ca++升高，或用新霉素间接抑制。通过在缺钙培养基中、加入乙二醇双四乙酸（EGTA）或存在Ca++通道阻滞剂维拉帕米的情况下培养卵母细胞来阻止细胞外Ca++内流。用BAPTA/AM预处理并随后在不添加外源Ca++的情况下培养，导致GVBD受到类似抑制（1 microM BAPTA/AM与未处理相比，P < 0.01）。卵泡释放后4小时，卵母细胞对BAPTA/AM处理不再敏感。新霉素也显著抑制GVBD（0.5 mM新霉素与未处理相比，P < 0.05）以及减数分裂超过中期I的进程（0.25 mM新霉素与未处理相比，P < 0.05）。当卵母细胞仅在缺钙培养基中培养或在EGTA或维拉帕米存在下培养时，GVBD的发生率没有显著影响。然而，通过降低培养基中的Ca++水平（0.68 mM Ca++与1.7 mM Ca++相比，P < 0.05）和用维拉帕米处理（0.25 mM维拉帕米与未处理相比，P < 0.05），减数分裂从GVBD到中期II的进程受到抑制。在0.85 mM EGTA存在下，减数分裂进程在中期I完全受阻。（摘要截断于250字）
