Secretion of surfactant protein A from rat type II pneumocytes

S. A. Rooney, L. I. Gobran, T. M. Umstead, David Phelps

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Secretion of surfactant phosphatidylcholine has been extensively studied and there is evidence that it is a regulated process that can be influenced by a variety of physiological factors and pharmacological agents. In contrast, secretion of the major surfactant protein, surfactant protein A (SP-A), has been investigated to much lesser extent. It is not known whether SP-A secretion is constitutive or regulated and, if regulated, whether its regulation is similar to that of phosphatidylcholine. To address those questions we measured SP-A secretion in primary cultures of type II pneumocytes under conditions identical to those used to study phosphatidylcholine secretion. Freshly isolated cells from adult rats were cultured overnight, washed, and then incubated in fresh medium in the presence and absence of surfactant phospholipid secretagogues. As previously reported for phosphatidylcholine, SP-A secretion was linear with time for up to 4 h. However, the rate of SP-A secretion, ~6% of total SP-A (cells + medium) released into the medium per hour, was more than sixfold greater than that of the lipid. Although freshly isolated cells contained 70% more SP-A than cells that were cultured overnight, the rate of SP-A secretion was not significantly different. Secretion of SP-A by freshly isolated or cultured type II cells was not increased by a combination of ATP, terbutaline, the adenosine A 2 receptor agonist 5'(N-ethylcarboxyamido)adenosine, 12-O- tetradecanoylphorbol-13-acetate, and ionomycin at concentrations that optimally stimulated phosphatidylcholine secretion. We conclude that secretion of the major lipid and protein components of surfactant are independently regulated.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume265
Issue number6 9-6
StatePublished - Dec 1 1993

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Pulmonary Surfactant-Associated Protein A
Alveolar Epithelial Cells
Phosphatidylcholines
Surface-Active Agents
Adenosine
Cultured Cells
Lipids
Terbutaline
Ionomycin
Tetradecanoylphorbol Acetate
varespladib methyl
Phospholipids
Proteins
Adenosine Triphosphate
Pharmacology

All Science Journal Classification (ASJC) codes

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology

Cite this

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title = "Secretion of surfactant protein A from rat type II pneumocytes",
abstract = "Secretion of surfactant phosphatidylcholine has been extensively studied and there is evidence that it is a regulated process that can be influenced by a variety of physiological factors and pharmacological agents. In contrast, secretion of the major surfactant protein, surfactant protein A (SP-A), has been investigated to much lesser extent. It is not known whether SP-A secretion is constitutive or regulated and, if regulated, whether its regulation is similar to that of phosphatidylcholine. To address those questions we measured SP-A secretion in primary cultures of type II pneumocytes under conditions identical to those used to study phosphatidylcholine secretion. Freshly isolated cells from adult rats were cultured overnight, washed, and then incubated in fresh medium in the presence and absence of surfactant phospholipid secretagogues. As previously reported for phosphatidylcholine, SP-A secretion was linear with time for up to 4 h. However, the rate of SP-A secretion, ~6{\%} of total SP-A (cells + medium) released into the medium per hour, was more than sixfold greater than that of the lipid. Although freshly isolated cells contained 70{\%} more SP-A than cells that were cultured overnight, the rate of SP-A secretion was not significantly different. Secretion of SP-A by freshly isolated or cultured type II cells was not increased by a combination of ATP, terbutaline, the adenosine A 2 receptor agonist 5'(N-ethylcarboxyamido)adenosine, 12-O- tetradecanoylphorbol-13-acetate, and ionomycin at concentrations that optimally stimulated phosphatidylcholine secretion. We conclude that secretion of the major lipid and protein components of surfactant are independently regulated.",
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Secretion of surfactant protein A from rat type II pneumocytes. / Rooney, S. A.; Gobran, L. I.; Umstead, T. M.; Phelps, David.

In: American Journal of Physiology - Lung Cellular and Molecular Physiology, Vol. 265, No. 6 9-6, 01.12.1993.

Research output: Contribution to journalArticle

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