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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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Related in: MedlinePlus

Time courses for the spironolactone-induced [Ca2+]i dynamics under channel blockers. (A) Effect of tetraethylammonium (TEA: 100 µM). (B) Effect of tetrodotoxin (TTX: 100 nM).
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Figure 6: Time courses for the spironolactone-induced [Ca2+]i dynamics under channel blockers. (A) Effect of tetraethylammonium (TEA: 100 µM). (B) Effect of tetrodotoxin (TTX: 100 nM).

Mentions: Spironolactone is an agonist of aldosterone, which affects the transport of Na+, K+ and Cl− in kidney epithelial cells. Therefore, we examined whether K+ or Na+ channels are correlated to the spironolactone-induced dynamics between [Ca2+]i and smooth muscles. Tetraethylammonium (100 µM) partially inhibited the spironolactone-induced initial increase in [Ca2+]i, but the following oscillatory fluctuations were observed (n=14) (Fig. 6A), indicating that the initial increase of spironolactone-induced [Ca2+]i dynamics were affected by K+ transport. Tetrodotoxin (TTX) binding physically blocks the flow of sodium ions through the channel, thereby preventing generation and propagation of action potential in excitable cells. TTX (100 µM) failed to inhibit the spironolactone-induced [Ca2+]i dynamics (n=13) (Fig. 6B), which suggests that the generation of action potential was not necessary for a spironolactone-induced response. Our arteriole specimens contained autonomic nerve endings, therefore spironolactone might stimulate nerve endings and the released neurotransmitters would elicit the [Ca2+]i dynamics, but the possibility can be excluded, because of the lack of an effect of TTX.


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)

Time courses for the spironolactone-induced [Ca2+]i dynamics under channel blockers. (A) Effect of tetraethylammonium (TEA: 100 µM). (B) Effect of tetrodotoxin (TTX: 100 nM).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Time courses for the spironolactone-induced [Ca2+]i dynamics under channel blockers. (A) Effect of tetraethylammonium (TEA: 100 µM). (B) Effect of tetrodotoxin (TTX: 100 nM).
Mentions: Spironolactone is an agonist of aldosterone, which affects the transport of Na+, K+ and Cl− in kidney epithelial cells. Therefore, we examined whether K+ or Na+ channels are correlated to the spironolactone-induced dynamics between [Ca2+]i and smooth muscles. Tetraethylammonium (100 µM) partially inhibited the spironolactone-induced initial increase in [Ca2+]i, but the following oscillatory fluctuations were observed (n=14) (Fig. 6A), indicating that the initial increase of spironolactone-induced [Ca2+]i dynamics were affected by K+ transport. Tetrodotoxin (TTX) binding physically blocks the flow of sodium ions through the channel, thereby preventing generation and propagation of action potential in excitable cells. TTX (100 µM) failed to inhibit the spironolactone-induced [Ca2+]i dynamics (n=13) (Fig. 6B), which suggests that the generation of action potential was not necessary for a spironolactone-induced response. Our arteriole specimens contained autonomic nerve endings, therefore spironolactone might stimulate nerve endings and the released neurotransmitters would elicit the [Ca2+]i dynamics, but the possibility can be excluded, because of the lack of an effect of TTX.

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