ATP and adenosine 3',5'-cyclic monophosphate stimulate the synthesis of surfactant protein A in rat lung.
Synthesis and secretion of surfactant protein A (SP-A) were studied in the isolated perfused rat lung using Trans35S-label (approximately 85% methionine, 15% cysteine) in the perfusate with or without 1 mM ATP or 0.1 mM 8-bromoadenosine 3',5',-cyclic monophosphate (8-BrcAMP) for up to 6 h of perfusion. By enzyme-linked immunosorbent assay, the SP-A content was 36 +/- 0.3% of total protein in extracellular surfactant and 10.8 +/- 1.9% of total protein in lamellar bodies of control lungs; these relativr proportions were maintained in the presence of ATP or 8-BrcAMP. Incorporation of [35S]methionine (cysteine) into the surfactant and lamellar body protein fraction could be detected at 4 h of perfusion. At 6 h, specific activity of total protein [disintegrations per minute (dpm)/micrograms)] was significantly increased in both the surfactant (54%) and lamellar body fractions (30%) under the influence of either secretagogue compared with control conditions. In the presence of ATP, there was a significant increase in the SP-A immunoprecipitable counts of 61 and 72% in extra- and intracellular compartments, respectively. However, no significant change was observed in the relative abundance of SP-A mRNA between control and secretagogue-treated lungs. This dissociation of SP-A mRNA abundance and label incorporation into protein indicates that alteration in translational efficiency or posttranslational factors may be involved in the secretagogue-induced stimulation of SP-A synthesis.
Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia.
A
A
Wali
M F
MF
Beers
C
C
Dodia
S I
SI
Feinstein
A B
AB
Fisher
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001345:Autoradiography; D015152:Blotting, Northern; D015153:Blotting, Western; D000242:Cyclic AMP / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000378:metabolism; D010477:Perfusion; D011510:Proteolipids / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013462:Sulfur Radioisotopes; D014404:Tubulin / Q000096:biosynthesis / Q000235:genetics
D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D013462:Sulfur Radioisotopes; D014404:Tubulin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000255:Adenosine Triphosphate; D008715:Methionine; D000242:Cyclic AMP