Sodium-calcium exchange and sidedness of isolated cardiac sarcolemmal vesicles

Donald M Bers, Kenneth D. Philipson, Ann Y. Nishimoto

Research output: Contribution to journalArticle

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Abstract

The sidedness of isolated rabbit cardiac sarcolemmal vesicles was studied by observing the effects of several permeability-increasing agents on measurements of the amount of sialic acid released by neuraminidase, specific ouabain binding, and K+-phosphatase and (Na+ + K+)-ATPase activities. The results suggest that the vesicles are sealed and are about 80% right-side-out. Na+-Ca2+ exchange exhibited by these vesicles could be attributed to the sarcolemma rather than to some contaminating organelle. Ca2+ uptake was stimulated by preloading the vesicles with NaCl (and not KCl). Increasing the external [Na+] induced a rapid Ca2+ loss, which could not be mimicked by K+, Li+, Rb+ or choline+. The Nai +-dependent Ca2+ uptake was inhibited by certain cations: Cd2+ > La3+ > Y3+ > Mn2+ > Co2+ > Mg2+. The Nai+-dependent Ca2+ influx was enhanced by an inside positive membrane potential and inhibited by an inside negative membrane potential. Potentials were induced by a K+-valinomycin system.

Original languageEnglish (US)
Pages (from-to)358-371
Number of pages14
JournalBBA - Biomembranes
Volume601
Issue numberC
DOIs
StatePublished - 1980

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Keywords

  • (Sarcolemmal vesicle)
  • Na-Ca exchange
  • Ouabain binding
  • Permeability
  • Sialic acid
  • Sidedness

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology
  • Medicine(all)

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