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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.

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Pseudocolor images and time course for spironolactone-induced [Ca2+]i dynamics. Note the biphasic [Ca2+]i dynamics; an initial acute increase (long arrow) was followed by a gradual decline with oscillatory fluctuations (small thick arrow).
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Figure 4: Pseudocolor images and time course for spironolactone-induced [Ca2+]i dynamics. Note the biphasic [Ca2+]i dynamics; an initial acute increase (long arrow) was followed by a gradual decline with oscillatory fluctuations (small thick arrow).

Mentions: When hydrochlorothiazide (100 µM) was added to the perfused HR, no dynamics of [Ca2+]i were detected (Fig. 2). Furosemide (100 µM) induced no significant [Ca2+]i dynamics (Fig. 3). To the contrary, spironolactone (300 µM) caused transient [Ca2+]i dynamics. The response of [Ca2+]i was biphasic; there was an initial rapid increase in [Ca2+]i, followed by a second gradual decline phase with fine oscillatory fluctuation (number of experiments; n=18) (Figs. 4, 5A). During the increase in [Ca2+]i, smooth muscles contraction was evident, and the external diameter decreased by approximately 20%.


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)

Pseudocolor images and time course for spironolactone-induced [Ca2+]i dynamics. Note the biphasic [Ca2+]i dynamics; an initial acute increase (long arrow) was followed by a gradual decline with oscillatory fluctuations (small thick arrow).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Pseudocolor images and time course for spironolactone-induced [Ca2+]i dynamics. Note the biphasic [Ca2+]i dynamics; an initial acute increase (long arrow) was followed by a gradual decline with oscillatory fluctuations (small thick arrow).
Mentions: When hydrochlorothiazide (100 µM) was added to the perfused HR, no dynamics of [Ca2+]i were detected (Fig. 2). Furosemide (100 µM) induced no significant [Ca2+]i dynamics (Fig. 3). To the contrary, spironolactone (300 µM) caused transient [Ca2+]i dynamics. The response of [Ca2+]i was biphasic; there was an initial rapid increase in [Ca2+]i, followed by a second gradual decline phase with fine oscillatory fluctuation (number of experiments; n=18) (Figs. 4, 5A). During the increase in [Ca2+]i, smooth muscles contraction was evident, and the external diameter decreased by approximately 20%.

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