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Article: Selectively inhibition of oxalate-stimulated Ca2+ transport by cyclopiazonic acid and thapsigargin in smooth muscle microsomes

TitleSelectively inhibition of oxalate-stimulated Ca2+ transport by cyclopiazonic acid and thapsigargin in smooth muscle microsomes
Authors
KeywordsSmooth muscle
Ca2+ pump
Cyclopiazonic acid
Thapsigargin
Sarcoplasmic reticulum
Issue Date1996
PublisherN R C Research Press. The Journal's web site is located at http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_desc_e?cjpp
Citation
Canadian Journal of Physiology and Pharmacology, 1996, v. 74, p. 182-192 How to Cite?
Abstract45Ca2+ uptake and efflux studies were performed on membranes prepared from dog mesenteric artery and rat vas deferens. Oxalate-stimulated, ATP-dependent Ca2+ uptake in microsomal vesicles, a property characteristic of sarcoplasmic reticulum, was completely inhibited in a concentration-dependent manner by cyclopiazonic acid (0.1-30 (iM) and thapsigargin (10 nM - 10 |xM). Using discontinuous sucrose gradient centrifugation, rat vas deferens microsomes were separated into two fractions, one enriched in plasma membrane (F2), the other enriched in sarcoplasmic reticulum (F3). The F3 fraction had a major increase in Ca2+ uptake in the presence of oxalate, which was completely inhibited by either cyclopiazonic acid or thapsigargin. In the F2 fraction Ca2+ uptake in the presence of oxalate was lower than in F3 and was not completely inhibited by thapsigargin and cyclopiazonic acid. Instead, the F2 fraction had a thapsigargin-insensitive and cyclopiazonic acid insensitive, saponin-sensitive component of uptake, which probably represents Ca2+ uptake by plasma membrane. In the absence of oxalate, the inhibition of Ca2+ uptake by saponin and cyclopiazonic acid or thapsigargin was additive in the F2 and F3 fractions, suggesting that cyclopiazonic acid and thapsigargin selectively inhibited sarcoplasmic reticulum derived Ca2+ uptake and did not affect plasma membrane derived Ca2+ uptake. Measurement of the initial rate of Ca2+ uptake in the presence and absence of oxalate by rat vas deferens microsomes demonstrated selective inhibition of oxalate-stimulated Ca2+ uptake by cyclopiazonic acid and thapsigargin. Ca2+ efflux from rat vas deferens microsomes actively loaded with 45Ca2+ either in the presence or the absence of oxalate was not increased by cyclopiazonic acid or thapsigargin, showing that the inhibition of Ca2+ accumulation was not due to an increase in Ca2+ efflux. In both rat vas deferens and dog mesenteric artery, the maximal inhibitory effects of cyclopiazonic acid developed rapidly, whereas for maximal inhibition thapsigargin required pretreatment of microsomes prior to measurement of Ca2+ uptake. In rat vas deferens microsomes the inhibitory effects of cyclopiazonic acid could be quickly and completely reversed, whereas the effects of thapsigargin were not easily reversed. Collectively, these results suggest selectivity of cyclopiazonic acid and thapsigargin for the sarcoplasmic reticulum Ca2+ pump. Their selective inhibitory properties and differences in onset and offset of inhibition make cyclopiazonic acid and thapsigargin useful pharmacological tools in the study of the physiological and pathophysiological roles of the sarcoplasmic reticulum Ca2+ pump in regulating smooth muscle Ca2+.
Persistent Identifierhttp://hdl.handle.net/10722/45289
ISSN
2015 Impact Factor: 1.704
2015 SCImago Journal Rankings: 0.683

 

DC FieldValueLanguage
dc.contributor.authorDarby, PJen_HK
dc.contributor.authorKwan, CYen_HK
dc.contributor.authorDaniel, EEen_HK
dc.date.accessioned2007-10-30T06:21:53Z-
dc.date.available2007-10-30T06:21:53Z-
dc.date.issued1996en_HK
dc.identifier.citationCanadian Journal of Physiology and Pharmacology, 1996, v. 74, p. 182-192en_HK
dc.identifier.issn0008-4212en_HK
dc.identifier.urihttp://hdl.handle.net/10722/45289-
dc.description.abstract45Ca2+ uptake and efflux studies were performed on membranes prepared from dog mesenteric artery and rat vas deferens. Oxalate-stimulated, ATP-dependent Ca2+ uptake in microsomal vesicles, a property characteristic of sarcoplasmic reticulum, was completely inhibited in a concentration-dependent manner by cyclopiazonic acid (0.1-30 (iM) and thapsigargin (10 nM - 10 |xM). Using discontinuous sucrose gradient centrifugation, rat vas deferens microsomes were separated into two fractions, one enriched in plasma membrane (F2), the other enriched in sarcoplasmic reticulum (F3). The F3 fraction had a major increase in Ca2+ uptake in the presence of oxalate, which was completely inhibited by either cyclopiazonic acid or thapsigargin. In the F2 fraction Ca2+ uptake in the presence of oxalate was lower than in F3 and was not completely inhibited by thapsigargin and cyclopiazonic acid. Instead, the F2 fraction had a thapsigargin-insensitive and cyclopiazonic acid insensitive, saponin-sensitive component of uptake, which probably represents Ca2+ uptake by plasma membrane. In the absence of oxalate, the inhibition of Ca2+ uptake by saponin and cyclopiazonic acid or thapsigargin was additive in the F2 and F3 fractions, suggesting that cyclopiazonic acid and thapsigargin selectively inhibited sarcoplasmic reticulum derived Ca2+ uptake and did not affect plasma membrane derived Ca2+ uptake. Measurement of the initial rate of Ca2+ uptake in the presence and absence of oxalate by rat vas deferens microsomes demonstrated selective inhibition of oxalate-stimulated Ca2+ uptake by cyclopiazonic acid and thapsigargin. Ca2+ efflux from rat vas deferens microsomes actively loaded with 45Ca2+ either in the presence or the absence of oxalate was not increased by cyclopiazonic acid or thapsigargin, showing that the inhibition of Ca2+ accumulation was not due to an increase in Ca2+ efflux. In both rat vas deferens and dog mesenteric artery, the maximal inhibitory effects of cyclopiazonic acid developed rapidly, whereas for maximal inhibition thapsigargin required pretreatment of microsomes prior to measurement of Ca2+ uptake. In rat vas deferens microsomes the inhibitory effects of cyclopiazonic acid could be quickly and completely reversed, whereas the effects of thapsigargin were not easily reversed. Collectively, these results suggest selectivity of cyclopiazonic acid and thapsigargin for the sarcoplasmic reticulum Ca2+ pump. Their selective inhibitory properties and differences in onset and offset of inhibition make cyclopiazonic acid and thapsigargin useful pharmacological tools in the study of the physiological and pathophysiological roles of the sarcoplasmic reticulum Ca2+ pump in regulating smooth muscle Ca2+.en_HK
dc.format.extent1979199 bytes-
dc.format.extent1844 bytes-
dc.format.mimetypeapplication/pdf-
dc.format.mimetypetext/plain-
dc.languageengen_HK
dc.publisherN R C Research Press. The Journal's web site is located at http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_desc_e?cjppen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsCanadian Journal of Physiology and Pharmacology. Copyright © N R C Research Press.en_HK
dc.subjectSmooth muscleen_HK
dc.subjectCa2+ pumpen_HK
dc.subjectCyclopiazonic aciden_HK
dc.subjectThapsigarginen_HK
dc.subjectSarcoplasmic reticulumen_HK
dc.titleSelectively inhibition of oxalate-stimulated Ca2+ transport by cyclopiazonic acid and thapsigargin in smooth muscle microsomesen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0008-4212&volume=74&spage=182&epage=192&date=1996&atitle=Selectively+inhibition+of+oxalate-stimulated+Ca2++transport+by+cyclopiazonic+acid+and+thapsigargin+in+smooth+muscle+microsomesen_HK
dc.description.naturepublished_or_final_versionen_HK
dc.identifier.hkuros26890-

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