Exposure of rabbit fetal lung to glucocorticoids in vitro does not enhance transcription of the gene encoding pulmonary surfactant-associated protein-B (SP-B).
We have investigated the ontogeny and hormonal regulation of both synthesis rates and cellular accumulation of the mRNA for surfactant-associated protein B (SP-B) in rabbit fetal lung. The developmental pattern for SP-B mRNA synthesis increased as a function of gestational age and paralleled that for SP-B mRNA levels except on days 22-26 of gestation where relatively higher levels of gene transcription were observed. Time-course studies with explants from 26- and 30-day fetal lung maintained in culture revealed a gradual increase in mRNA levels and a much smaller increase in gene transcription relative to adult values. Within 48 h of exposure of 26-day explants to dexamethasone at 10(-8) M there was a rapid increase in SP-B mRNA levels to 7-fold adult levels. A similar overall although somewhat slower and attenuated pattern was observed with 30-day explants. Dexamethasone at 10(-8) M had no effect on SP-B gene transcription with explants of either gestational age. We conclude that the major effect of dexamethasone treatment in vitro on SP-B mRNA levels appears to be post-transcriptional and there are small but distinct differences in the effects of glucocorticoids on SP-B mRNA levels with explant cultures from early and late stages of fetal lung maturation.
Xu
J
J
MRC Group in Fetal and Neonatal Health and Development, University of Western Ontario, University Hospital, London, Canada.
Possmayer
F
F
D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005325:Fetal Organ Maturity; D005865:Gestational Age; D005938:Glucocorticoids / Q000494:pharmacology*; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D011510:Proteolipids / Q000235:genetics*; D011663:Pulmonary Surfactants / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D014158:Transcription, Genetic / Q000187:drug effects
D005938:Glucocorticoids; D011510:Proteolipids; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; D003907:Dexamethasone