Registration of small (below 1%) changes of calcium ion concentration in aqueous solutions and in serum by the constant potential coulometric method

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.

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Fura-2 fluorescence is localized to mitochondria in endothelial cells

AJP Cell Physiology ◽

10.1152/ajpcell.1987.253.5.c744 ◽

1987 ◽

Vol 253 (5) ◽

pp. C744-C747 ◽

Cited By ~ 64

Author(s):

S. F. Steinberg ◽

J. P. Bilezikian ◽

Q. Al-Awqati

Keyword(s):

Endothelial Cells ◽

Calcium Ion ◽

Cytosolic Calcium ◽

Ion Concentration ◽

Homogeneous Distribution ◽

Aortic Endothelial Cells ◽

Fura 2 ◽

Bovine Aortic Endothelial Cells ◽

Calcium Ion Concentration ◽

Aortic Endothelial

The new, highly fluorescent, calcium-sensitive dye, fura-2, can be loaded nondisruptively into intact cells by means of its permeant ester and used to measure the free calcium ion concentration in individual cells. For fura-2 to signal cytosolic calcium, it must be distributed homogeneously and exclusively throughout the cytoplasmic space. However, microscopic examination of bovine aortic endothelial cells loaded with fura-2 by exposure to its permeant ester reveals fluorescence associated with discrete intracellular structures rather than the homogeneous distribution expected for a cytosolic stain. Simultaneous labeling of bovine aortic endothelial cells with fura-2 and rhodamine 123 (a mitochondrial fluorescent vital stain) identifies these structures as mitochondria. Subcellular dye localizations are not observed when the cells are loaded with other putative cytosolic stains that gain access to the cytosol by means of a membrane permeant ester. Both carboxyfluorescein and indo-1 (another member of the family of second generation calcium indicators) stain the cytoplasm diffusely. It is suggested that fura-2 fluorescence accumulates in certain cells in association with mitochondria. It is important to assess the intracellular distribution of fura-2 when this indicator is used to measure the free cytosolic calcium ion concentration.

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