The effects of cyclopiazonic acid on intracellular Ca2+ in aortic smooth muscle cells from DOCA-hypertensive rats

R. C.A. Tostes, D. W. Wilde, L. M. Bendhack, R Clinton Webb

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

We tested the hypothesis that cyclopiazonic acid (CPA), an inhibitor of the sarcoplasmic reticulum (SR) Ca2+-ATPaSe, increases intracellular Ca2+ concentration ([Ca2+]i) in aortic myocytes and that the increase in [Ca2+]i is higher in aortic cells from deoxycorticosterone acetate (DOCA)-hypertensive rats. Male Sprague-Dawley rats, 250-300 g, underwent uninephrectomy, received a silastic implant containing DOCA (200 mg/kg) and had free access to water supplemented with 1.0% NaCl and 0.2% KCI. Control rats were also uninephrectomized, received normal tap water, but no implant. Intracellular Ca2+ measurements were performed in aortic myocytes isolated from normotensive (Systolic blood pressure = 120 ± 3 mmHg; body weight = 478 ± 7 g, N = 7) and DOCA-hypertensive rats (195 ± 10 mmHg; 358 ± 16 g, N = 7). The effects of CPA on resting [Ca2+]i and on caffeine-induced increase in [Ca2+]i after [Ca2+]i depletion and reloading were compared in aortic cells from DOCA and normotensive rats. The phasic increase in [Ca2+]i induced by 20 mM caffeine in Ca2+-free buffer was significantly higher in DOCA aortic cells (329 ± 36 nM, N = 5) compared to that in normotensive cells (249 ± 16 nM, N = 7, P<0.05). CPA (3 μM) inhibited caffeine-induced increases in [Ca2+]i in both groups. When the cells were placed in normal buffer (1.6 mM Ca2+, loading period), after treatment with Ca2+-free buffer (depletion period), an increase in [Ca2+]i was observed in DOCA aortic cells (45 ± 11 nM, N = 5) while no changes were observed in normotensive cells. CPA (3 μM) potentiated the increase in [Ca2+]i (122 ± 30 nM, N = 5) observed in DOCA cells during the loading period while only a modest increase in [Ca2+]i (23 ± 10 nM, N = 5) was observed in normotensive cells. CPA-induced increase in [Ca2+]i did not occur in the absence of extracellular Ca2+ or in the presence of nifedipine. These data show that CPA induces Ca2+ influx in aorta from both normotensive and DOCA-hypertensive rats. However, the increase in [Ca2+]i is higher in DOCA aortic cells possibly due to an impairment in the mechanisms that control [Ca2+]i. The large increase in [Ca2+]i in response to caffeine in DOCA cells probably reflects a greater storage Of Ca2+ in the SR.

Original languageEnglish (US)
Pages (from-to)257-267
Number of pages11
JournalBrazilian Journal of Medical and Biological Research
Volume30
Issue number2
DOIs
StatePublished - Jan 1 1997
Externally publishedYes

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Desoxycorticosterone
Smooth Muscle Myocytes
Muscle
Rats
Acetates
Cells
Caffeine
Buffers
Sarcoplasmic Reticulum
Muscle Cells
Rat control
cyclopiazonic acid
Blood Pressure
Water
Blood pressure
Nifedipine
Sprague Dawley Rats
Aorta
Body Weight

Keywords

  • Caffeine
  • Cyclopiazonic acid
  • Deoxycorticosterone (DOCA) hypertension
  • Intracellular calcium mobilization
  • Sarcoplasmic reticulum
  • Vascular smooth muscle

ASJC Scopus subject areas

  • Biophysics
  • Neuroscience(all)
  • Biochemistry
  • Physiology
  • Immunology
  • Pharmacology, Toxicology and Pharmaceutics(all)
  • Cell Biology

Cite this

The effects of cyclopiazonic acid on intracellular Ca2+ in aortic smooth muscle cells from DOCA-hypertensive rats. / Tostes, R. C.A.; Wilde, D. W.; Bendhack, L. M.; Webb, R Clinton.

In: Brazilian Journal of Medical and Biological Research, Vol. 30, No. 2, 01.01.1997, p. 257-267.

Research output: Contribution to journalArticle

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T1 - The effects of cyclopiazonic acid on intracellular Ca2+ in aortic smooth muscle cells from DOCA-hypertensive rats

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AU - Webb, R Clinton

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N2 - We tested the hypothesis that cyclopiazonic acid (CPA), an inhibitor of the sarcoplasmic reticulum (SR) Ca2+-ATPaSe, increases intracellular Ca2+ concentration ([Ca2+]i) in aortic myocytes and that the increase in [Ca2+]i is higher in aortic cells from deoxycorticosterone acetate (DOCA)-hypertensive rats. Male Sprague-Dawley rats, 250-300 g, underwent uninephrectomy, received a silastic implant containing DOCA (200 mg/kg) and had free access to water supplemented with 1.0% NaCl and 0.2% KCI. Control rats were also uninephrectomized, received normal tap water, but no implant. Intracellular Ca2+ measurements were performed in aortic myocytes isolated from normotensive (Systolic blood pressure = 120 ± 3 mmHg; body weight = 478 ± 7 g, N = 7) and DOCA-hypertensive rats (195 ± 10 mmHg; 358 ± 16 g, N = 7). The effects of CPA on resting [Ca2+]i and on caffeine-induced increase in [Ca2+]i after [Ca2+]i depletion and reloading were compared in aortic cells from DOCA and normotensive rats. The phasic increase in [Ca2+]i induced by 20 mM caffeine in Ca2+-free buffer was significantly higher in DOCA aortic cells (329 ± 36 nM, N = 5) compared to that in normotensive cells (249 ± 16 nM, N = 7, P<0.05). CPA (3 μM) inhibited caffeine-induced increases in [Ca2+]i in both groups. When the cells were placed in normal buffer (1.6 mM Ca2+, loading period), after treatment with Ca2+-free buffer (depletion period), an increase in [Ca2+]i was observed in DOCA aortic cells (45 ± 11 nM, N = 5) while no changes were observed in normotensive cells. CPA (3 μM) potentiated the increase in [Ca2+]i (122 ± 30 nM, N = 5) observed in DOCA cells during the loading period while only a modest increase in [Ca2+]i (23 ± 10 nM, N = 5) was observed in normotensive cells. CPA-induced increase in [Ca2+]i did not occur in the absence of extracellular Ca2+ or in the presence of nifedipine. These data show that CPA induces Ca2+ influx in aorta from both normotensive and DOCA-hypertensive rats. However, the increase in [Ca2+]i is higher in DOCA aortic cells possibly due to an impairment in the mechanisms that control [Ca2+]i. The large increase in [Ca2+]i in response to caffeine in DOCA cells probably reflects a greater storage Of Ca2+ in the SR.

AB - We tested the hypothesis that cyclopiazonic acid (CPA), an inhibitor of the sarcoplasmic reticulum (SR) Ca2+-ATPaSe, increases intracellular Ca2+ concentration ([Ca2+]i) in aortic myocytes and that the increase in [Ca2+]i is higher in aortic cells from deoxycorticosterone acetate (DOCA)-hypertensive rats. Male Sprague-Dawley rats, 250-300 g, underwent uninephrectomy, received a silastic implant containing DOCA (200 mg/kg) and had free access to water supplemented with 1.0% NaCl and 0.2% KCI. Control rats were also uninephrectomized, received normal tap water, but no implant. Intracellular Ca2+ measurements were performed in aortic myocytes isolated from normotensive (Systolic blood pressure = 120 ± 3 mmHg; body weight = 478 ± 7 g, N = 7) and DOCA-hypertensive rats (195 ± 10 mmHg; 358 ± 16 g, N = 7). The effects of CPA on resting [Ca2+]i and on caffeine-induced increase in [Ca2+]i after [Ca2+]i depletion and reloading were compared in aortic cells from DOCA and normotensive rats. The phasic increase in [Ca2+]i induced by 20 mM caffeine in Ca2+-free buffer was significantly higher in DOCA aortic cells (329 ± 36 nM, N = 5) compared to that in normotensive cells (249 ± 16 nM, N = 7, P<0.05). CPA (3 μM) inhibited caffeine-induced increases in [Ca2+]i in both groups. When the cells were placed in normal buffer (1.6 mM Ca2+, loading period), after treatment with Ca2+-free buffer (depletion period), an increase in [Ca2+]i was observed in DOCA aortic cells (45 ± 11 nM, N = 5) while no changes were observed in normotensive cells. CPA (3 μM) potentiated the increase in [Ca2+]i (122 ± 30 nM, N = 5) observed in DOCA cells during the loading period while only a modest increase in [Ca2+]i (23 ± 10 nM, N = 5) was observed in normotensive cells. CPA-induced increase in [Ca2+]i did not occur in the absence of extracellular Ca2+ or in the presence of nifedipine. These data show that CPA induces Ca2+ influx in aorta from both normotensive and DOCA-hypertensive rats. However, the increase in [Ca2+]i is higher in DOCA aortic cells possibly due to an impairment in the mechanisms that control [Ca2+]i. The large increase in [Ca2+]i in response to caffeine in DOCA cells probably reflects a greater storage Of Ca2+ in the SR.

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KW - Cyclopiazonic acid

KW - Deoxycorticosterone (DOCA) hypertension

KW - Intracellular calcium mobilization

KW - Sarcoplasmic reticulum

KW - Vascular smooth muscle

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