Surfactant protein B metabolism in newborn rabbits.
Surfactant protein B (SP-B) is critical to the biophysical function of surfactant. To characterize its metabolism in vivo in the newborn, we administered [35S]methionine and [3H]palmitate to newborn rabbits intravascularly. Three groups of 4 rabbits per group were killed at each of 4 time points followed by isolation of SP-B from alveolar wash and lamellar bodies. The labeling kinetics for alveolar wash associated SP-B and saturated phosphatidylcholine (Sat PC) had similar patterns. To characterize SP-B clearance from the airspace, rabbit SP-B was iodinated, mixed with [14C]dipalmitoylphosphatidylcholine and given by intratracheal injection. Alveolar washes and lamellar bodies were recovered from 4 animals at each of 7 time points. Both SP-B and Sat PC were cleared slowly from the total lung (half-life values approximately 25 h). However, SP-B was cleared more rapidly from the airspaces than was Sat PC. The ratio of [125I]SP-B to [14C]Sat PC in lamellar bodies increased 2-fold by 8 h. These results support the concept of linked secretion and clearance pathways for SP-B and Sat PC, although small differences in reuptake were detected.
Henry
M
M
Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, CA 90509, USA.
Ikegami
M
M
Ueda
T
T
Jobe
A
A
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000008:administration & dosage / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D007700:Kinetics; D008168:Lung / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D011510:Proteolipids / Q000008:administration & dosage / Q000302:isolation & purification / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000008:administration & dosage / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D014132:Trachea / Q000378:metabolism
D010169:Palmitic Acids; D011510:Proteolipids; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine; D019308:Palmitic Acid; D008715:Methionine