Appearance of surfactant proteins, SP-A and SP-B, in developing rat lung and the effects of in vivo dexamethasone treatment.
Hydrophobic pulmonary surfactant proteins (SP-B and SP-C) promote the adsorption of phospholipids at the air/liquid interface and the addition of surfactant protein A (SP-A) enhances this function. The developmental profiles of phospholipids and SP-A in the lung have been reported, but that of SP-B and SP-C remain unknown. We recently developed an enzyme-linked immunosorbent assay (ELISA) that measures SP-B in the rat. Using ELISA for SP-A and SP-B, we measured the contents of SP-A and SP-B in lung homogenates. The developmental profiles of SP-A and SP-B during the late gestational and postnatal periods were found to be distinctly different from each other. SP-A increased during late gestation and reached its maximum on day 1 after birth. This developmental profile of SP-A in the lungs was very similar to that of disaturated phosphatidylcholine (DSPC). In contrast, the SP-B contents in fetal lungs were low and increased after birth, reaching its maximum on day 4 after birth. In vivo dexamethasone treatment resulted in significant increases of SP-A content in rat lung homogenate on day 19 and day 21 of gestation, and day 5 after birth, whereas SP-B content increased significantly only on day 19 of gestation by dexamethasone administration. SP-A synthesis may be enhanced both pre- and postnatally, but SP-B synthesis may be stimulated only during the late gestational period by in vivo dexamethasone treatment. The difference in developmental profiles and the different responses to dexamethasone treatment between SP-A and SP-B indicate that the expression of SP-A and SP-B may be regulated independently at least in developing rat lungs.
Shimizu
H
H
Department of Biochemistry, Sapporo Medical College, Japan.
Miyamura
K
K
Kuroki
Y
Y
D000375:Aging; D000595:Amino Acid Sequence; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005865:Gestational Age; D006023:Glycoproteins / Q000096:biosynthesis; D008168:Lung / Q000187:drug effects / Q000196:embryology / Q000254:growth & development*; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000378:metabolism; D011510:Proteolipids / Q000096:biosynthesis* / Q000302:isolation & purification; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis* / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
D006023:Glycoproteins; D010713:Phosphatidylcholines; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D003907:Dexamethasone