Sarcoplasmic reticulum Ca2+ uptake is not decreased in aorta from deoxycorticosterone acetate hypertensive rats: Functional assessment with cyclopiazonic acid

R. C.A. Tostes, O. Traub, L. M. Bendhack, R Clinton Webb

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Ca2+ plays a major role in vascular contraction, and a defect in intracellular Ca2+ regulation has been associated with increased vascular reactivity in hypertension. To test the hypothesis that the sarcoplasmic reticulum does not adequately buffer Ca2+ in deoxycorticosterone acetate (DOCA) hypertension, contractile experiments were performed with a specific inhibitor of the sarcoplasmic reticulum Ca2+ ATPase, cyclopiazonic acid (CPA). Contractile force in aortic strips from DOCA and control rats was measured, using standard muscle bath procedures, to evaluate (i) Ca2+ handling, assessing caffeine and serotonin (5HT) induced contractions in Ca2+-free buffer and (ii) relaxation rate after 5HT washout. Contractile responses elicited with 5HT (3 x 10-6 mol/L) and caffeine (20 mmol/L) were greater in DOCA than in control arteries. CPA (1 x 10-7 to 3 x 10-5 mol/L) reduced phasic contractions to 5HT and caffeine in DOCA and control aorta, and no differences in the IC50 values were observed. Aortae from DOCA rats contracted when placed in normal buffer, subsequent to treatment with Ca2+-free buffer, but control aortae did not. CPA potentiated these responses in DOCA aorta and only caused a modest contraction in control aorta. CPA-induced contraction did not occur in Ca2+-free buffer, and it was inhibited by nifedipine (IC50 = 4 x 10-9 mol/L). The relaxation rate, after 5HT washout (3 x 10-6 mol/L), was increased in DOCA aorta (2.6 ± 0.3 min) compared with control (17 ± 0.2 min), and CPA (10-5 mol/L) increased the relaxation rate in both groups. The results support the hypothesis of defective Ca2+ handling in DOCA hypertension. However, an increased Ca2+ influx, and not a decreased buffering ability of the sarcoplasmic reticulum, contributes to the enhanced vascular reactivity observed in DOCA hypertension.

Original languageEnglish (US)
Pages (from-to)1536-1545
Number of pages10
JournalCanadian Journal of Physiology and Pharmacology
Volume73
Issue number11
DOIs
StatePublished - Jan 1 1995
Externally publishedYes

Fingerprint

Desoxycorticosterone
Sarcoplasmic Reticulum
Aorta
Acetates
Buffers
Caffeine
Hypertension
Blood Vessels
Inhibitory Concentration 50
cyclopiazonic acid
Calcium-Transporting ATPases
Nifedipine
Baths
Serotonin
Arteries
Muscles

Keywords

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

ASJC Scopus subject areas

  • Physiology
  • Pharmacology
  • Physiology (medical)

Cite this

@article{12bcf21929a1435b9536184d9871cdb6,
title = "Sarcoplasmic reticulum Ca2+ uptake is not decreased in aorta from deoxycorticosterone acetate hypertensive rats: Functional assessment with cyclopiazonic acid",
abstract = "Ca2+ plays a major role in vascular contraction, and a defect in intracellular Ca2+ regulation has been associated with increased vascular reactivity in hypertension. To test the hypothesis that the sarcoplasmic reticulum does not adequately buffer Ca2+ in deoxycorticosterone acetate (DOCA) hypertension, contractile experiments were performed with a specific inhibitor of the sarcoplasmic reticulum Ca2+ ATPase, cyclopiazonic acid (CPA). Contractile force in aortic strips from DOCA and control rats was measured, using standard muscle bath procedures, to evaluate (i) Ca2+ handling, assessing caffeine and serotonin (5HT) induced contractions in Ca2+-free buffer and (ii) relaxation rate after 5HT washout. Contractile responses elicited with 5HT (3 x 10-6 mol/L) and caffeine (20 mmol/L) were greater in DOCA than in control arteries. CPA (1 x 10-7 to 3 x 10-5 mol/L) reduced phasic contractions to 5HT and caffeine in DOCA and control aorta, and no differences in the IC50 values were observed. Aortae from DOCA rats contracted when placed in normal buffer, subsequent to treatment with Ca2+-free buffer, but control aortae did not. CPA potentiated these responses in DOCA aorta and only caused a modest contraction in control aorta. CPA-induced contraction did not occur in Ca2+-free buffer, and it was inhibited by nifedipine (IC50 = 4 x 10-9 mol/L). The relaxation rate, after 5HT washout (3 x 10-6 mol/L), was increased in DOCA aorta (2.6 ± 0.3 min) compared with control (17 ± 0.2 min), and CPA (10-5 mol/L) increased the relaxation rate in both groups. The results support the hypothesis of defective Ca2+ handling in DOCA hypertension. However, an increased Ca2+ influx, and not a decreased buffering ability of the sarcoplasmic reticulum, contributes to the enhanced vascular reactivity observed in DOCA hypertension.",
keywords = "Caffeine, Cyclopiazonic acid, Deoxycorticosterone (DOCA) hypertension, Intracellular calcium mobilization, Sarcoplasmic reticulum, Vascular smooth muscle",
author = "Tostes, {R. C.A.} and O. Traub and Bendhack, {L. M.} and Webb, {R Clinton}",
year = "1995",
month = "1",
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T1 - Sarcoplasmic reticulum Ca2+ uptake is not decreased in aorta from deoxycorticosterone acetate hypertensive rats

T2 - Functional assessment with cyclopiazonic acid

AU - Tostes, R. C.A.

AU - Traub, O.

AU - Bendhack, L. M.

AU - Webb, R Clinton

PY - 1995/1/1

Y1 - 1995/1/1

N2 - Ca2+ plays a major role in vascular contraction, and a defect in intracellular Ca2+ regulation has been associated with increased vascular reactivity in hypertension. To test the hypothesis that the sarcoplasmic reticulum does not adequately buffer Ca2+ in deoxycorticosterone acetate (DOCA) hypertension, contractile experiments were performed with a specific inhibitor of the sarcoplasmic reticulum Ca2+ ATPase, cyclopiazonic acid (CPA). Contractile force in aortic strips from DOCA and control rats was measured, using standard muscle bath procedures, to evaluate (i) Ca2+ handling, assessing caffeine and serotonin (5HT) induced contractions in Ca2+-free buffer and (ii) relaxation rate after 5HT washout. Contractile responses elicited with 5HT (3 x 10-6 mol/L) and caffeine (20 mmol/L) were greater in DOCA than in control arteries. CPA (1 x 10-7 to 3 x 10-5 mol/L) reduced phasic contractions to 5HT and caffeine in DOCA and control aorta, and no differences in the IC50 values were observed. Aortae from DOCA rats contracted when placed in normal buffer, subsequent to treatment with Ca2+-free buffer, but control aortae did not. CPA potentiated these responses in DOCA aorta and only caused a modest contraction in control aorta. CPA-induced contraction did not occur in Ca2+-free buffer, and it was inhibited by nifedipine (IC50 = 4 x 10-9 mol/L). The relaxation rate, after 5HT washout (3 x 10-6 mol/L), was increased in DOCA aorta (2.6 ± 0.3 min) compared with control (17 ± 0.2 min), and CPA (10-5 mol/L) increased the relaxation rate in both groups. The results support the hypothesis of defective Ca2+ handling in DOCA hypertension. However, an increased Ca2+ influx, and not a decreased buffering ability of the sarcoplasmic reticulum, contributes to the enhanced vascular reactivity observed in DOCA hypertension.

AB - Ca2+ plays a major role in vascular contraction, and a defect in intracellular Ca2+ regulation has been associated with increased vascular reactivity in hypertension. To test the hypothesis that the sarcoplasmic reticulum does not adequately buffer Ca2+ in deoxycorticosterone acetate (DOCA) hypertension, contractile experiments were performed with a specific inhibitor of the sarcoplasmic reticulum Ca2+ ATPase, cyclopiazonic acid (CPA). Contractile force in aortic strips from DOCA and control rats was measured, using standard muscle bath procedures, to evaluate (i) Ca2+ handling, assessing caffeine and serotonin (5HT) induced contractions in Ca2+-free buffer and (ii) relaxation rate after 5HT washout. Contractile responses elicited with 5HT (3 x 10-6 mol/L) and caffeine (20 mmol/L) were greater in DOCA than in control arteries. CPA (1 x 10-7 to 3 x 10-5 mol/L) reduced phasic contractions to 5HT and caffeine in DOCA and control aorta, and no differences in the IC50 values were observed. Aortae from DOCA rats contracted when placed in normal buffer, subsequent to treatment with Ca2+-free buffer, but control aortae did not. CPA potentiated these responses in DOCA aorta and only caused a modest contraction in control aorta. CPA-induced contraction did not occur in Ca2+-free buffer, and it was inhibited by nifedipine (IC50 = 4 x 10-9 mol/L). The relaxation rate, after 5HT washout (3 x 10-6 mol/L), was increased in DOCA aorta (2.6 ± 0.3 min) compared with control (17 ± 0.2 min), and CPA (10-5 mol/L) increased the relaxation rate in both groups. The results support the hypothesis of defective Ca2+ handling in DOCA hypertension. However, an increased Ca2+ influx, and not a decreased buffering ability of the sarcoplasmic reticulum, contributes to the enhanced vascular reactivity observed in DOCA hypertension.

KW - Caffeine

KW - Cyclopiazonic acid

KW - Deoxycorticosterone (DOCA) hypertension

KW - Intracellular calcium mobilization

KW - Sarcoplasmic reticulum

KW - Vascular smooth muscle

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