Observations on intracellular pH during cleavage of eggs of Xenopus laevis.

Abstract

Direct measurements of intracellular pH was made with recessed-tip pH microelectrodes in fertilized eggs of the frog, Xenopus laevis, from approximately 1 h after fertilization to mid-blastula. The intracellular pH just before first cleavage was 7.65 +/- 0.04 (SD; n = 9). By stage 5 to the middle of stage 6, average intracellular pH was 7.70 +/- 0.06 (SD; n = 16). A statistically significant alkalization of 0.18 +/- 0.03 pH unit (SD; n = 5) was observed beginning in early blastula. A cycle of less than or equal to 0.05 pH unit was occasionally observed during the pre-blastula period, but its significance is unknown. By exposing the early cleavage embryo to saline buffered with sodium propionate, pH 4.7-5.0, it was possible to lower intracellular pH with some degree of control. Apparently, normal cleavage continued to occur when intracellular pH had been forced as much as 0.3 unit below normal. We conclude that this implies no specific involvement of intracellular pH in mitosis and cytokinesis. If intracellular pH was lowered further, cell division ceased at about pH 7.2, and furrow regression began at about pH 7.0. Once furrow regression occurred, subsequent development was usually arrested or abnormal when the embryo was transferred back to normal saline.

Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates

“…For example, pH gates gap junctions (Greenfield et al, 1990;Turin and Warner, 1980), which are essential for normal LR axis development (Levin and Mercola, 1999). pH regulation also has a role in gene expression and differentiation (Sater et al, 1994;Uzman et al, 1998) and in other important developmental processes such as proliferation, apoptosis and growth factor release (Bidani et al, 1998;Lee and Steinhardt, 1981;Putney and Barber, 2003;Shrode et al, 1997). pH also has other physiological effects that are likely to be important during development, although a direct connection has not been shown.…”

Regulation of intracellular pH in eukaryotic cells

“…Experiments with early Xenopus embryos indicated, however, that pH, is not necessarily a universal regulator of mitosis. It was reported that even if small oscillations in pHi occurred during the mitotic cycle in early Xenopus embryos, no delay in mitosis occurred when the pHi was artificially reduced (Lee & Steinhardt, 1981). Furthermore, clamping at high pHi values did not interfere with normal chromosome cycling or cell division in the sea urchin embryo (Grainger et al, 1979).…”

Unidirectional microtubule assembly in cell‐free extracts of Spisula solidissima oocytes is regulated by subtle changes in pH

“…The rhythmicity of the pH, oscillations has been well characterized in Xenopus embryos [Lee and Steinhardt, 1981;Webb and Nuccitelli, 1982;Grandin and Charbonneau, 19901. Fertilization of Xenopus eggs is accompanied by a permanent increase in the intracellular pH followed by a periodic fluctuation in pH,.…”

“…Changes in intracellular pH (pH,) are associated with a variety of cellular growth control mechanisms [Busa, 1986;Roos and Boron, 1981;Rozengurt, 19861. For example, systematic changes in pH, occur during the cell cycle progression from interphase to mitosis [Gerson and Burton, 1977;Musgrove et al, 1987;Taylor and Hodson, 1984;Bright et al, 19871. The rhythmicity of the pH, oscillations has been well characterized in Xenopus embryos [Lee and Steinhardt, 1981;Webb and Nuccitelli, 1982;Grandin and Charbonneau, 19901. Fertilization of Xenopus eggs is accompanied by a permanent increase in the intracellular pH followed by a periodic fluctuation in pH,.…”