title: Pulmonary surfactant and its components inhibit secretion of phosphatidylcholine from cultured rat alveolar type II cells.
abstract: Pulmonary surfactant is synthesized and secreted by alveolar type II cells. Radioactive phosphatidylcholine has been used as a marker for surfactant secretion. We report findings that suggest that surfactant inhibits secretion of 3H-labeled phosphatidylcholine by cultured rat type II cells. The lipid components and the surfactant protein group of Mr 26,000-36,000 (SP 26-36) inhibit secretion to different extents. Surfactant lipids do not completely inhibit release; in concentrations of 100 micrograms/ml, lipids inhibit stimulated secretion by 40%. SP 26-36 inhibits release with an EC50 of 0.1 microgram/ml. At concentrations of 1.0 microgram/ml, SP 26-36 inhibits basal secretion and reduces to basal levels secretion stimulated by terbutaline, phorbol 12-myristate 13-acetate, and the ionophore A23187. The inhibitory effect of SP 26-36 can be blocked by washing type II cells after adding SP 26-36, by heating the proteins to 100 degrees C for 10 min, by adding antiserum specific to SP 26-36, or by incubating cells in the presence of 0.2 mM EGTA. SP 26-36 isolated from canine and human sources also inhibits phosphatidylcholine release from rat type II cells. Neither type I collagen nor serum apolipoprotein A-1 inhibits secretion. These findings are compatible with the hypothesis that surfactant secretion is under feedback regulatory control.
authors.forename: L G
authors.initials: LG
authors.lastname: Dobbs
authors.forename: J R
authors.initials: JR
authors.lastname: Wright
authors.forename: S
authors.initials: S
authors.lastname: Hawgood
authors.forename: R
authors.initials: R
authors.lastname: Gonzalez
authors.forename: K
authors.initials: K
authors.lastname: Venstrom
authors.forename: J
authors.initials: J
authors.lastname: Nellenbogen
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004285:Dogs; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008055:Lipids / Q000494:pharmacology; D008081:Liposomes / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011506:Proteins / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D001059:Apoproteins; D008055:Lipids; D008081:Liposomes; D010713:Phosphatidylcholines; D011506:Proteins; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; C046616:pulmonary surfactant apoprotein; D007770:L-Lactate Dehydrogenase