Effects of inhibiting protein synthesis on the secretion of surfactant by type II cells in primary culture

Richard J. King, Helen M. Martin

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Pulmonary surfactant is isolated from the alveolar lumen as a complex of lipid and protein (King R.J. (1974) Fed. Proc. 23, 2238-2247) and is probably secreted as such (King R.J., Martin H., Mitts D. and Holmstrom F.M. (1977) J. Appl. Physiol. 42, 483-491). We wished to determine whether the secretion of this complex was dependent upon cellular activities associated with the synthesis of protein, and whether the pre-formed lipids of surfactant would be released from the cell even though the synthesis of newly-formed protein was inhibited. Alveolar epithelial Type II cells were isolated from adult rat lung and grown to confluency in primary culture. The synthesis and secretion of the apolipoprotein of surfactant and its principal lipid, dipalmitoyl phosphatidyl-choline, were followed by isotopic precursor techniques. The synthesis of the apolipoprotein was reduced to 14% of control by 1 · 10-4 M cycloheximide and to 2.5% of control by 4 · 10-4 M cycloheximide. These concentrations of cycloheximide, however, had no effect on the rate of synthesis or release of DPPC. The secretion of the apolipoprotein which had been synthesized before the addition of 1 · 10-4 M cycloheximide was not inhibited by this compound. Cells maintained at 5°C neither synthesized nor released surfactant. We conclude, therefore, that the synthesis of cellular protein is not required for the secretion of surfactant, but that the continuous generation of metabolic energy may be essential. These results, together with those of previous kinetic studies (see above references), suggest that the lipid and protein constituents of surfactant may be contained within lamellar bodies prior to their release into the extracellular environment.

Original languageEnglish (US)
Pages (from-to)289-301
Number of pages13
JournalBiochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
Volume663
Issue number1
DOIs
StatePublished - Jan 26 1981

Keywords

  • (Type II cell)
  • Apolipoprotein
  • Dipalmitoyl phosphatidylcholine
  • Lipid metabolism
  • Protein synthesis
  • Pulmonary surfactant

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Endocrinology

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