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The effects of diuretics on intracellular Ca2+ dynamics of arteriole smooth muscles as revealed by laser confocal microscopy.

Tamagawa Y, Saino T, Matsuura M, Satoh Y - Acta Histochem Cytochem (2009)

Bottom Line: Diuretics may regulate intracellular Ca(2+) concentration ([Ca(2+)](i)) and have an effect on vascular tone.In this study, hydrochlorothiazide (100 microM) and furosemide (100 microM) had no effect on the [Ca(2+)](i) dynamics.Tetrodotoxin, a neurotoxic Na(+) channel blocker, had no effect, therefore the spironolactone-induced dynamics is a direct effect to smooth muscles, rather than an indirect effect via vessel nerves.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy (Cell Biology), School of Medicine, Iwate Medical University, Morioka 020-8505, Japan.

ABSTRACT
The regulation of cytosolic Ca(2+) homeostasis is essential for cells, including vascular smooth muscle cells. Arterial tone, which underlies the maintenance of peripheral resistance in the circulation, is a major contributor to the control of blood pressure. Diuretics may regulate intracellular Ca(2+) concentration ([Ca(2+)](i)) and have an effect on vascular tone. In order to investigate the influence of diuretics on peripheral resistance in circulation, we investigated the alteration of [Ca(2+)](i) in testicular arterioles with respect to several categories of diuretics using real-time confocal laser scanning microscopy. In this study, hydrochlorothiazide (100 microM) and furosemide (100 microM) had no effect on the [Ca(2+)](i) dynamics. However, when spironolactone (300 microM) was applied, the [Ca(2+)](i) of smooth muscles increased. The response was considerably inhibited under either extracellular Ca(2+)-free conditions, the presence of Gd(3+), or with a treatment of diltiazem. After the thapsigargin-induced depletion of internal Ca(2+) store, the spironolactone-induced [Ca(2+)](i) dynamics was slightly inhibited. Therefore, the spironolactone-induced dynamics of [Ca(2+)](i) can be caused by either a Ca(2+) influx from extracellular fluid or Ca(2+) mobilization from internal Ca(2+) store, with the former being dominant. As tetraethylammonium, an inhibitor of the K(+) channel, slightly inhibited the spironolactone-induced [Ca(2+)](i) dynamics, the K(+) channel might play a minor role in those dynamics. Tetrodotoxin, a neurotoxic Na(+) channel blocker, had no effect, therefore the spironolactone-induced dynamics is a direct effect to smooth muscles, rather than an indirect effect via vessel nerves.

No MeSH data available.


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Arteriole specimens from testicular tissue used in the present study. (A) Scanning electron micrograph. Bar=100 µm. (B) Confocal fluorescent image showing indo-1 ratio pseudocolor. Smooth muscles were shown as spindle-shaped profiles and maintained a circular arrangement. Damaged cells with a high [Ca2+]i level were rare, ensuring functional integrity of the specimen. Bar=100 µm, Color scale bar=fluorescence ratio represents [Ca2+]i.
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Figure 1: Arteriole specimens from testicular tissue used in the present study. (A) Scanning electron micrograph. Bar=100 µm. (B) Confocal fluorescent image showing indo-1 ratio pseudocolor. Smooth muscles were shown as spindle-shaped profiles and maintained a circular arrangement. Damaged cells with a high [Ca2+]i level were rare, ensuring functional integrity of the specimen. Bar=100 µm, Color scale bar=fluorescence ratio represents [Ca2+]i.

Mentions: Images of arterioles by SEM and real-time confocal laser scanning microscopy are shown in Figure 1. Arterioles were surrounded by spindle-shaped smooth muscles in a circular fashion. There was little morphological deterioration following the isolation procedures. Confocal laser scanning microscopy provided clear images showing smooth muscle profiles. Images obtained by ratiometry showed that the [Ca2+]i in the arterioles was stable and that their ratio was about 0.5 in the absence of agonists.


The effects of diuretics on intracellular Ca2+ dynamics of arteriole smooth muscles as revealed by laser confocal microscopy.

Tamagawa Y, Saino T, Matsuura M, Satoh Y - Acta Histochem Cytochem (2009)

Arteriole specimens from testicular tissue used in the present study. (A) Scanning electron micrograph. Bar=100 µm. (B) Confocal fluorescent image showing indo-1 ratio pseudocolor. Smooth muscles were shown as spindle-shaped profiles and maintained a circular arrangement. Damaged cells with a high [Ca2+]i level were rare, ensuring functional integrity of the specimen. Bar=100 µm, Color scale bar=fluorescence ratio represents [Ca2+]i.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2742722&req=5

Figure 1: Arteriole specimens from testicular tissue used in the present study. (A) Scanning electron micrograph. Bar=100 µm. (B) Confocal fluorescent image showing indo-1 ratio pseudocolor. Smooth muscles were shown as spindle-shaped profiles and maintained a circular arrangement. Damaged cells with a high [Ca2+]i level were rare, ensuring functional integrity of the specimen. Bar=100 µm, Color scale bar=fluorescence ratio represents [Ca2+]i.
Mentions: Images of arterioles by SEM and real-time confocal laser scanning microscopy are shown in Figure 1. Arterioles were surrounded by spindle-shaped smooth muscles in a circular fashion. There was little morphological deterioration following the isolation procedures. Confocal laser scanning microscopy provided clear images showing smooth muscle profiles. Images obtained by ratiometry showed that the [Ca2+]i in the arterioles was stable and that their ratio was about 0.5 in the absence of agonists.

Bottom Line: Diuretics may regulate intracellular Ca(2+) concentration ([Ca(2+)](i)) and have an effect on vascular tone.In this study, hydrochlorothiazide (100 microM) and furosemide (100 microM) had no effect on the [Ca(2+)](i) dynamics.Tetrodotoxin, a neurotoxic Na(+) channel blocker, had no effect, therefore the spironolactone-induced dynamics is a direct effect to smooth muscles, rather than an indirect effect via vessel nerves.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy (Cell Biology), School of Medicine, Iwate Medical University, Morioka 020-8505, Japan.

ABSTRACT
The regulation of cytosolic Ca(2+) homeostasis is essential for cells, including vascular smooth muscle cells. Arterial tone, which underlies the maintenance of peripheral resistance in the circulation, is a major contributor to the control of blood pressure. Diuretics may regulate intracellular Ca(2+) concentration ([Ca(2+)](i)) and have an effect on vascular tone. In order to investigate the influence of diuretics on peripheral resistance in circulation, we investigated the alteration of [Ca(2+)](i) in testicular arterioles with respect to several categories of diuretics using real-time confocal laser scanning microscopy. In this study, hydrochlorothiazide (100 microM) and furosemide (100 microM) had no effect on the [Ca(2+)](i) dynamics. However, when spironolactone (300 microM) was applied, the [Ca(2+)](i) of smooth muscles increased. The response was considerably inhibited under either extracellular Ca(2+)-free conditions, the presence of Gd(3+), or with a treatment of diltiazem. After the thapsigargin-induced depletion of internal Ca(2+) store, the spironolactone-induced [Ca(2+)](i) dynamics was slightly inhibited. Therefore, the spironolactone-induced dynamics of [Ca(2+)](i) can be caused by either a Ca(2+) influx from extracellular fluid or Ca(2+) mobilization from internal Ca(2+) store, with the former being dominant. As tetraethylammonium, an inhibitor of the K(+) channel, slightly inhibited the spironolactone-induced [Ca(2+)](i) dynamics, the K(+) channel might play a minor role in those dynamics. Tetrodotoxin, a neurotoxic Na(+) channel blocker, had no effect, therefore the spironolactone-induced dynamics is a direct effect to smooth muscles, rather than an indirect effect via vessel nerves.

No MeSH data available.


Related in: MedlinePlus