Cycling of intracellular free calcium and intracellular pH in Xenopus embryos: a possible role in the control of the cell cycle

1991 ◽  
Vol 99 (1) ◽  
pp. 5-11
Author(s):  
N Grandin ◽  
M Charbonneau
Keyword(s):  
Cell Cycle ◽  
Intracellular Ph ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Xenopus Embryos

scholarly journals Intracellular free calcium oscillates during cell division of Xenopus embryos.

1991 ◽  
Vol 112 (4) ◽  
pp. 711-718 ◽  
Author(s):  
N Grandin ◽  
M Charbonneau
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Volume ◽  
Intracellular Ph ◽  
Calcium Ions ◽  
Volume Ratio ◽  
Mean Amplitude ◽  
Free Calcium ◽  
Periodic Oscillations ◽  
Xenopus Embryos

In Xenopus embryos, previous results failed to detect changes in the activity of free calcium ions (Ca2+i) during cell division using Ca2(+)-selective microelectrodes, while experiments with aequorin yielded uncertain results complicated by the variation during cell division of the aequorin concentration to cell volume ratio. We now report, using Ca2(+)-selective microelectrodes, that cell division in Xenopus embryos is accompanied by periodic oscillations of the Ca2+i level, which occur with a periodicity of 30 min, equal to that of the cell cycle. These Ca2+i oscillations were detected in 24 out of 35 experiments, and had a mean amplitude of 70 nM, around a basal Ca2+i level of 0.40 microM. Ca2+i oscillations did not take place in the absence of cell division, either in artificially activated eggs or in cleavage-blocked embryos. Therefore, Ca2+i oscillations do not represent, unlike intracellular pH oscillations (Grandin, N., and M. Charbonneau. J. Cell Biol. 111:523-532. 1990), a component of the basic cell cycle ("cytoplasmic clock" or "master oscillator"), but appear to be more likely related to some events of mitosis.

Intracellular pH and intracellular free calcium responses to protein kinase C activators and inhibitors in Xenopus eggs

Development ◽  
1991 ◽  
Vol 112 (2) ◽  
pp. 461-470 ◽  
Author(s):  
N. Grandin ◽  
M. Charbonneau
Keyword(s):  
Cell Cycle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Ph ◽  
Phorbol Esters ◽  
Intracellular Free Calcium ◽  
Egg Activation ◽  
Cortical Granule ◽  
Free Calcium ◽  
Kinase C

Cell activation during fertilization of the egg of Xenopus laevis is accompanied by various metabolic changes, including a permanent increase in intracellular pH (pHi) and a transient increase in intracellular free calcium activity ([Ca2+]i). Recently, it has been proposed that protein kinase C (PKC) is an integral component of the Xenopus fertilization pathway (Bement and Capco, J. Cell Biol. 108, 885–892, 1989). Indeed, activators of PKC trigger cortical granule exocytosis and cortical contraction, two events of egg activation, without, however, releasing the cell cycle arrest (blocked in second metaphase of meiosis). In the egg of Xenopus, exocytosis as well as cell cycle reinitiation are supposed to be triggered by the intracellular Ca2+ transient. We report here that PKC activators do not induce the intracellular Ca2+ transient, or the activation-associated increase in pHi. These results suggest that the ionic responses to egg activation in Xenopus do not appear to depend on the activation of PKC. In addition, in eggs already pretreated with phorbol esters, those artificial activators that act by releasing Ca2+ intracellularly, triggered a diminished increase in pHi. Finally, sphingosine and staurosporine, two potent inhibitors of PKC, were found to trigger egg activation, suggesting that a decrease in PKC activity might be an essential event in the release of the metaphase block, in agreement with recent findings on the release of the prophase block in Xenopus oocytes (Varnold and Smith, Development 109, 597–604, 1990).

The increase in intracellular pH associated with Xenopus egg activation is a Ca(2+)-dependent wave

1992 ◽  
Vol 101 (1) ◽  
pp. 55-67 ◽  
Author(s):  
N. Grandin ◽  
M. Charbonneau
Keyword(s):  
Cell Cycle ◽  
Intracellular Ph ◽  
Egg Activation ◽  
Free Calcium ◽  
Slowing Down ◽  
M Phase ◽  
Xenopus Egg ◽  
General Slowing ◽  
The Impact ◽  
Kinetics Of

In Xenopus eggs, the transient increase in intracellular free calcium ([Ca2+]i), or Ca2+ transient, which occurs 1–3 min after egg activation, is likely to be partly responsible for the release of the cell cycle blockade. In the present study, we have used microinjection of BAPTA or EGTA, two potent chelators of Ca2+, to buffer [Ca2+]i at various steps during Xenopus egg activation and evaluate the impact on some of the associated events. Microinjection of either one of the Ca2+ chelators into unactivated eggs prevented egg activation without, however, lowering [Ca2+]i, suggesting that only physiological [Ca2+]i changes, but not [Ca2+]i levels, were affected by the Ca2+ buffer. When BAPTA was microinjected around the time of occurrence of the Ca2+ transient, the egg activation-associated increase in intracellular pH (pHi) was clearly delayed. That delay was not due to a general slowing down of the cell cycle, since under the same conditions of microinjection of BAPTA the kinetics of MPF (a universal M-phase promoting factor) inactivation were unaffected. These results represent the first indication that the Ca2+ transient participates in determining the time of initiation of the pHi increase during Xenopus egg activation. The present results also demonstrate that the egg activation-associated pHi changes (a slight, transient decrease in pHi followed by a permanent increase in pHi) proceed as a wave propagating from the site of triggering of egg activation. Experiments of local microinjection of BAPTA support the view that the pH wave is a consequence of the Ca2+ wave, which it follows closely.

scholarly journals Superoxide anion increases intracellular pH, intracellular free calcium, and arachidonate release in human amnion cells

1991 ◽  
Vol 266 (20) ◽  
pp. 13233-13237
Author(s):  
Y. Ikebuchi ◽  
N. Masumoto ◽  
K. Tasaka ◽  
K. Koike ◽  
K. Kasahara ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Superoxide Anion ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Human Amnion ◽  
Arachidonate Release

Enhanced Effects of Insulin and Angiotensin II on Intracellular pH and Free Cytosolic Calcium in Fibroblasts from Microalbuminuric Patients with Non-Insulin-Dependent Diabetes Mellitus

1996 ◽  
Vol 91 (6) ◽  
pp. 703-710 ◽  
Author(s):  
R. Trevisan ◽  
E. Duner ◽  
M. R. Cipollina ◽  
F. Di Virgilio ◽  
M. Trevisan ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Angiotensin Ii ◽  
Intracellular Ph ◽  
Insulin Dependent Diabetes Mellitus ◽  
Insulin Dependent Diabetes ◽  
Intracellular Free Calcium ◽  
Dependent Diabetes Mellitus ◽  
Free Calcium ◽  
Control Subjects ◽  
Insulin Dependent

1. Whether an alteration in cell membrane cation transport after exposure to insulin and angiotensin II (two important growth promoters that have been shown to be involved in the pathogenesis of atherosclerosis and hypertension) is present in cells from non-insulin-dependent diabetes patients with microalbuminuria, a known risk factor for cardiovascular and renal disease, is unknown. We therefore examined intracellular pH and calcium changes after acute exposure to insulin and angiotensin II in cultured skin fibroblasts from eight non-insulin-dependent diabetes patients with and eight others without microalbuminuria and from a group of seven matched, normal control subjects. 2. Cultured fibroblasts were loaded with 2′,7′-bis (2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester or fura 2-acetoxymethyl ester for continuous monitoring of intracellular pH and free calcium concentrations respectively. 3. In quiescent growth-arrested cells, both intracellular pH and free calcium concentrations were similar in the three groups of subjects. Acutely, insulin induced a gradual alkalinization in all groups of patients. The pH increase was significantly greater in non-insulin-dependent diabetes mellitus patients with microalbuminuria (ΔpH +0.24 ± 0.04 pH units) than in normoalbuminuric patients with non-insulin-dependent diabetes mellitus (0.08 ± 0.02; P < 0.01) and normal control subjects (0.05 ± 0.01; P < 0.01). Although the alkalinizing effect of angiotensin II was smaller than that obtained by insulin, intracellular pH increase after angiotensin addition was more pronounced in non-insulin-dependent diabetes mellitus patients with microalbuminuria (ΔpH ± 0.14 ± 0.04 pH units) than in those without (0.08 ± 0.02; P < 0.01) and in normal control subjects (0.02 ± 0.02; P < 0.01). That the increase in intracellular pH was mediated by the sodium—hydrogen antiport was demonstrated by its dependence on the presence of sodium in the medium and its inhibition by amiloride. Whereas insulin addition did not evoke any significant increase in intracellular free calcium levels in fibroblasts from the three groups studied, angiotensin II evoked a fast and transient rise in intracellular free calcium that was higher in fibroblasts from microalbuminuric patients with non-insulin-dependent diabetes mellitus than in cells from normoalbuminuric patients with non-insulin-dependent diabetes mellitus and control subjects. In the whole population of patients with non-insulin-dependent diabetes mellitus, the increase in intracellular pH after exposure to angiotensin II was positively correlated with intracellular free calcium increase (r = 0.53; P < 0.05), suggesting a possible role of intracellular free calcium levels in the activation of the sodium—hydrogen antiport. 4. In conclusion, we have described an association between increased agonist-induced responsiveness of sodium—hydrogen antiport activity and the presence of microalbuminuria in patients with non-insulin-dependent diabetes mellitus. This increased responsiveness, persisting in cultured fibroblasts after several passages in vitro, suggests that in vitro phenotypic characteristics of fibroblasts are likely to be genetically determined and to be, at least in part, independent of the degree of metabolic control in vivo.

scholarly journals Superoxide anion increases intracellular free calcium in human myometrial cells.

1990 ◽  
Vol 265 (36) ◽  
pp. 22533-22536
Author(s):  
N Masumoto ◽  
K Tasaka ◽  
A Miyake ◽  
O Tanizawa
Keyword(s):  
Superoxide Anion ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Myometrial Cells
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