Woodruff R I, Telfer W H
Department of Biology, West Chester University, PA 19383.
Arch Insect Biochem Physiol. 1994;25(1):9-20. doi: 10.1002/arch.940250103.
Intracellular activities of K+, H+, Mg2+, Ca2+, and Cl-, measured with ion selective microelectrodes in the oocyte and the nurse cells in ovarian follicles of Hyalophora cecropia, indicated that a Ca2+ current is a key component of the electrical potential that is maintained across the intercellular bridges connecting these two cells. In vitellogenic follicles, Ca2+ activity averaged 650 nM in the oocyte and 190 nM in the nurse cells, whereas activities of the other ions studied differed between these cells by no more than 6%. Incubation in 200 microM ammonium vanadate caused a reversal of electrical potential from 8.3 mV, nurse cell negative, to 3.0 mV, oocyte negative, and at the same time the Ca2+ gradient was reversed: activities rose to an average 3.0 microM in the nurse cells and 1.6 microM in the oocyte, whereas transbridge ratios of the other cations remained at 0-3%. In immature follicles that had not yet initiated their transbridge potentials, Ca2+ activities averaged approximately 2 microM in both oocyte and nurse cells. The results suggest that vitellogenic follicles possess a vanadate-sensitive Ca2+ extrusion mechanism that is more powerful in the nurse cells than in the oocyte.
用离子选择性微电极测量天蚕蛾卵巢卵泡中卵母细胞和滋养细胞内的K⁺、H⁺、Mg²⁺、Ca²⁺和Cl⁻活性，结果表明Ca²⁺电流是维持连接这两个细胞的细胞间桥两端电势的关键组成部分。在卵黄生成卵泡中，卵母细胞内Ca²⁺活性平均为650 nM，滋养细胞内为190 nM，而所研究的其他离子在这些细胞中的活性差异不超过6%。在200 μM钒酸铵中孵育导致电势从8.3 mV（滋养细胞为负）反转至3.0 mV（卵母细胞为负），同时Ca²⁺梯度也发生反转：滋养细胞内活性升至平均3.0 μM，卵母细胞内为1.6 μM，而其他阳离子的跨桥比率保持在0 - 3%。在尚未产生跨桥电势的未成熟卵泡中，卵母细胞和滋养细胞内Ca²⁺活性平均约为2 μM。结果表明，卵黄生成卵泡具有一种对钒酸盐敏感的Ca²⁺外排机制，该机制在滋养细胞中比在卵母细胞中更强大。
