Ca2+ displacement by polymyxin B from sarcolemma isolated by 'gas dissection' from cultured neonatal rat myocardial cells

Janis M. Burt, Glenn A. Langer

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Amphiphilic, cationic Polymyxin B is shown to displace Ca2+ from 'gas dissected' cardiac sarcolemma in a dose-dependent, saturable fashion. The Ca2+ displacement is only partially reversible, 57% and 63%, in the presence of 1 mM or 10 mM Ca2+, respectively. Total Ca2+ displaced by a non-specific cationic probe, lanthanum (La3+), at maximal displacing concentration (1 mM) was 0.172 ± 0.02 nmol/μg membrane protein. At 0.1 mM, Polymyxin B displaced 42% of the total La3+-displaceable Ca2+ or 0.072 ± 0.01 nmol/μg protein. 5 mM Polymyxin displaced Ca2+ in amounts equal to those displaced by 1 mM La3+. Pretreatment of the membranes with neuraminidase (removal of sialic acid) and protease leads to a decrease in La3+-displaceable Ca2+ but to an increase in the fraction displaced by 0.1 mM Polymyxin from 42% to 54%. Phospholipase D (cabbage) treatment significantly increased the La3+-displaceable Ca2+ to 0.227 ± 0.02 nmol/μg protein (P < 0.05), a gain of 0.055 nmol. All of this phospholipid specific increment in bound Ca2+ was displaced by 0.1 mM Polymyxin B. The results suggest that Polymyxin B will be useful as a probe for phospholipid Ca2+-binding sites in natural membranes.

Original languageEnglish (US)
Pages (from-to)44-52
Number of pages9
JournalBBA - Biomembranes
Volume729
Issue number1
DOIs
StatePublished - Mar 23 1983
Externally publishedYes

Keywords

  • (Rat myocardial cell membrane)
  • Ca binding site
  • Ca displacement
  • La
  • Polymyxin B

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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