Surfactant protein A metabolism in preterm ventilated lambs.
Surfactant protein A (SP-A) metabolism was studied in vivo in 33 preterm ventilated lambs at 138 +/- 1 days gestational age by measuring recoveries of exogenously administered surfactant containing both radiolabeled SP-A and labeled saturated phosphatidylcholine (Sat PC) given via the trachea at birth. Endogenously secreted SP-A was also labeled with [35S]methionine and followed over 24 h. The exogenously labeled SP-A left the alveolar pool more rapidly than did Sat PC over the first 5 h of life (P less than 0.05), and both exogenously labeled SP-A and Sat PC were detected within lamellar bodies by 2 h, indicating uptake from the airspaces. The quantity of SP-A in alveolar washes increased about twofold from birth to 5 h of age, whereas alveolar Sat PC pools were constant over 24 h. The SP-A endogenously labeled with [35S]methionine was recovered at highest specific activities in the alveolar washes at 10 and 45 min after birth with no labeled SP-A detectable in lamellar body fractions until 2 h. The curve for endogenous SP-A labeling of lamellar bodies was similar to that for exogenous labeling, indicating that SP-A was initially secreted by a pathway independent of lamellar bodies with subsequent SP-A labeling of lamellar bodies. The kinetics of SP-A metabolism were very different than for Sat PC in preterm lambs.
Ikegami
M
M
Department of Pediatrics, Harbor-University of California, Los Angeles Medical Center, School of Medicine, Torrance 90509.
Lewis
J F
JF
Tabor
B
B
Rider
E D
ED
Jobe
A H
AH
D000818:Animals; D000831:Animals, Newborn; D002585:Cesarean Section; D002846:Chromatography, Affinity; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007700:Kinetics; D008168:Lung / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D011510:Proteolipids / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D012121:Respiration, Artificial; D012127:Respiratory Distress Syndrome, Newborn / Q000378:metabolism; D012756:Sheep; D013462:Sulfur Radioisotopes; D014316:Tritium
D010713:Phosphatidylcholines; D010761:Phosphorus Radioisotopes; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D013462:Sulfur Radioisotopes; D014316:Tritium; D008715:Methionine