scholarly journals Oscillatory membrane potential changes in cells of mesenchymal origin: the role of an intracellular calcium regulating system

1979 ◽  
Vol 81 (1) ◽  
pp. 49-61
Author(s):  
P. G. Nelson ◽  
M. P. Henkart
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Potential ◽  
Intracellular Calcium ◽  
Calcium Ion ◽  
Surface Membrane ◽  
Ion Concentration ◽  
Free Calcium ◽  
Potassium Ions ◽  
Calcium Ion Concentration

A number of mesenchymal cells (fibroblasts, macrophages and megakaryocytes) respond to a variety of stimuli with large hyperpolarizations lasting several seconds (the H.A. response). The H.A. responses can occur as repetitive trains or oscillations. These hyperpolarizations are due to an increase of the surface membrane permeability to potassium ions which is probably mediated by an increase in the cytoplasmic free calcium ion concentration. Evidence is discussed which suggests that the source of this increased calcium, is least in part, an intracellular sequestering system, probably the endoplasmic reticulum. A model capable of producing oscillatory changes in membrane potential is proposed based on such an intracellular calcium sequestering and releasing system.

scholarly journals Cytosolic free calcium-ion concentration in cleaving embryonic cells of Oryzias latipes measured with calcium-selective microelectrodes.

1985 ◽  
Vol 100 (3) ◽  
pp. 947-954 ◽  
Author(s):  
A R Schantz
Keyword(s):  
Membrane Potential ◽  
Calcium Ion ◽  
Oryzias Latipes ◽  
Potassium Acetate ◽  
Ion Concentration ◽  
Free Calcium ◽  
Embryonic Cells ◽  
Cell Stage ◽  
Partial Digestion ◽  
Calcium Ion Concentration

Calcium-selective microelectrodes were used to measure the free calcium-ion concentration ([Ca2+]i) in early-cleaving embryonic cells of the golden medaka, Oryzias latipes, a fresh water teleost fish. Embryos could be dechorionated as early as the four-cell stage using a three-step technique consisting of removal of some yolk to enlarge the perivitelline space, partial digestion of the chorion with pancreatin, and removal of the weakened chorion with forceps. Dechorionated embryos underwent cleavage at a normal rate. Intracellular cytosolic [Ca2+]i was monitored by impaling blastomeres first with a microelectrode filled with 5 M potassium acetate to measure membrane potential, and a few minutes later with a calcium-selective microelectrode. During nine rounds of cytokinesis from a total of six different embryos, cytosolic [Ca2+]i remained constant (with apparently random fluctuations of less than +/- 0.1 microM). During two successive cleavages in one embryo, however, [Ca2+]i rose transiently fourfold above the original resting level to 1.32 and 1.20 microM in synchrony with each period of cytokinesis and returned after each rise to submicromolar levels. Because a calcium-selective microelectrode can detect [Ca2+]i changes only in the immediate vicinity of its 2-microns tip, we interpreted these data to suggest that, although [Ca2+]i in most areas of the cytosol remains between 0.01 and 0.40 microM (mean of 0.14 microM), there may be small regions of the cell in which [Ca2+]i undergoes a substantial increase at the time of cleavage. Evidence also is presented to suggest that the membrane potential in these blastomeres undergoes a slow net hyperpolarization during early cleavage stages.

scholarly journals Injection of inositol trisphosphorothioate into Limulus ventral photoreceptors causes oscillations of free cytosolic calcium.

1991 ◽  
Vol 97 (6) ◽  
pp. 1165-1186 ◽  
Author(s):  
R Payne ◽  
B V Potter
Keyword(s):  
Membrane Potential ◽  
Calcium Release ◽  
Feedback Inhibition ◽  
Initial Response ◽  
Periodic Variation ◽  
Cytosolic Calcium ◽  
Ion Concentration ◽  
Free Calcium ◽  
Calcium Stores ◽  
Calcium Ion Concentration

Limulus ventral photoreceptors contain calcium stores sensitive to release by D-myo-inositol 1,4,5 trisphosphate (InsP3) and a calcium-activated conductance that depolarizes the cell. Mechanisms that terminate the response to InsP3 were investigated using nonmetabolizable DL-myo-inositol 1,4,5 trisphosphorothioate (InsPS3). An injection of 1 mM InsPS3 into a photoreceptor's light-sensitive lobe caused an initial elevation of cytosolic free calcium ion concentration (Cai) and a depolarization lasting only 1-2 s. A period of densensitization followed, during which injections of InsPS3 were ineffective. As sensitivity recovered, oscillations of membrane potential began, continuing for many minutes with a frequency of 0.07-0.3 Hz. The activity of InsPS3 probably results from the D-stereoisomer, since L-InsP3 was much less effective than InsP3. Injections of 1 mM InsP3 caused an initial depolarization and a period of densensitization similar to that caused by 1 mM InsPS3, but no sustained oscillations of membrane potential. The initial response to InsPS3 or InsP3 may therefore be terminated by densensitization, rather than by metabolism. Metabolism of InsP3 may prevent oscillations of membrane potential after sensitivity has recovered. The InsPS3-induced oscillations of membrane potential accompanied oscillations of Cai and were abolished by injection of ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid. Removal of extracellular calcium reduced the frequency of oscillation but not its amplitude. Under voltage clamp, oscillations of inward current were observed. These results indicate that periodic bursts of calcium release underly the oscillations of membrane potential. After each burst, the sensitivity of the cell to injected InsP3 was greatly reduced, recovering during the interburst interval. The oscillations may, therefore, result in part from a periodic variation in sensitivity to a constant concentration of InsPS3. Prior injection of calcium inhibited depolarization by InsPS3, suggesting that feedback inhibition of InsPS3-induced calcium release by elevated Cai may mediate desensitization between bursts and after injections of InsPS3.

Bile canalicular contraction in the isolated hepatocyte doublet is related to an increase in cytosolic free calcium ion concentration

2008 ◽  
Vol 8 (3) ◽  
pp. 178-183 ◽  
Author(s):  
Sumio Watanabe ◽  
Masahiro Tomono ◽  
Makoto Takeuchi ◽  
Tsuneo Kitamura ◽  
Miyoko Hirose ◽  
...  
Keyword(s):  
Calcium Ion ◽  
Ion Concentration ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Bile Canalicular Contraction ◽  
Calcium Ion Concentration

scholarly journals The gravistimulation-induced very slow Ca2+ increase in Arabidopsis seedlings requires MCA1, a Ca2+-permeable mechanosensitive channel

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Masataka Nakano ◽  
Takuya Furuichi ◽  
Masahiro Sokabe ◽  
Hidetoshi Iida ◽  
Hitoshi Tatsumi
Keyword(s):  
Calcium Ion ◽  
Channel Blocker ◽  
Upright Position ◽  
Ion Concentration ◽  
Early Event ◽  
Free Calcium ◽  
Permeable Channel ◽  
Mechanosensitive Ion Channel ◽  
And Function ◽  
Calcium Ion Concentration

AbstractGravity is a critical environmental factor affecting the morphology and function of plants on Earth. Gravistimulation triggered by changes in the gravity vector induces an increase in the cytoplasmic free calcium ion concentration ([Ca2+]c) as an early process of gravity sensing; however, its role and molecular mechanism are still unclear. When seedlings of Arabidopsis thaliana expressing apoaequorin were rotated from the upright position to the upside-down position, a biphasic [Ca2+]c-increase composed of a fast-transient [Ca2+]c-increase followed by a slow [Ca2+]c-increase was observed. We find here a novel type [Ca2+]c-increase, designated a very slow [Ca2+]c-increase that is observed when the seedlings were rotated back to the upright position from the upside-down position. The very slow [Ca2+]c-increase was strongly attenuated in knockout seedlings defective in MCA1, a mechanosensitive Ca2+-permeable channel (MSCC), and was partially restored in MCA1-complemented seedlings. The mechanosensitive ion channel blocker, gadolinium, blocked the very slow [Ca2+]c-increase. This is the first report suggesting the possible involvement of MCA1 in an early event related to gravity sensing in Arabidopsis seedlings.

Dependence of Cardiac Contractility on Myofibrillar Calcium Sensitivity

Physiology ◽  
1987 ◽  
Vol 2 (5) ◽  
pp. 179-182
Author(s):  
JC Ruegg
Keyword(s):  
Calcium Ion ◽  
Sarcomere Length ◽  
Cardiac Contractility ◽  
Calcium Sensitivity ◽  
Ion Concentration ◽  
Free Calcium ◽  
Wide Range ◽  
Heart Contractility ◽  
Calcium Ion Concentration

In the heart, contractility may be varied over a wide range. It is determined mainly by the myoplasmic free calcium ion concentration. However, alteration of the responsiveness of the myofilaments to calcium may also be important in regulating cardiac contractility, in particular following changes in sarcomere length, or in hypoxia, or after interventions with certain novel cardiotonic drugs.

Sign in / Sign up

Export Citation Format

Share Document