Maintenance of epithelial surface membrane lipid polarity: A role for differing phospholipid translocation rates

Bruce A. Molitoris, Francis R. Simon

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Large differences in lipid composition of apical and basolateral membranes from epithelial cells exist. To determine the responsible mechanism(s), rat renal cortical brush border and basolateral membrane phospholipids were labeled using32P and either [3H]-glycerol or [2-3H] acetate for incorporation and degradation studies, respectively. Brush border and basolateral membrane fractions were isolated simultaneously from the same cortical homogenate. Different phospholipid classes were degraded at variable rates with phosphatidylcholine having the fastest decay rate. Decay rates for individual phospholipid classes were, however, similar in both brush border and basolateral membrane fractions. In phospholipid incorporation studies again, large variations existed between individual phospholipid classes with phosphatidylcholine and phosphatidylinositol showing the most rapid rates of incorporation. Sphingomyelin and phosphatidylserine showed extremely slow incorporation rates and did not enter into the isotopic decay phase for 48 hr. In contrast to degradation studies, however, the same phospholipid class labeled the two surface membrane domains at highly variable rates. The difference in these rates, with the exception of phosphatidylinositol, were identical to the differences in phospholipid compositions between the two membranes. For example, phosphatidylcholine was incorporated into the basolateral membrane 2.5 × faster than into the brush border membrane and its relative composition was 2.5 × greater in the basolateral membrane. The opposite was true for sphingomyelin. These results indicate incorporation and not degradation rates of individual phospholipids play a major role in regulating the differing phospholipid composition of brush border and basolateral membranes.

Original languageEnglish (US)
Pages (from-to)47-53
Number of pages7
JournalThe Journal of Membrane Biology
Volume94
Issue number1
DOIs
StatePublished - Feb 1 1986
Externally publishedYes

Keywords

  • basolateral membrane
  • brush border membrane
  • epithelial polarity
  • phospholipids

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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