Nicotine stimulates branching and expression of SP-A and SP-C mRNAs in embryonic mouse lung culture

Although the effects of maternal smoking on fetal growth and viability are overwhelmingly negative, there is a paradoxical enhancement of lung maturation as evidenced, in part, by a lower incidence of respiratory distress syndrome in infants of smoking mothers. Other epidemiologic and experimental evidence further support the view that a tobacco smoke constituent, possibly nicotine, affects the development of the lung in utero. We are studying the direct effects of nicotine on murine lung development using a serumless organ culture system. We have found that embryonic lungs explanted at 11 days gestation showed a 32% increase in branching after 4 days in culture in the presence of 1 microM nicotine and 7- to 15-fold increases in mRNAs encoding surfactant proteins A and C after 11 days. The effect of nicotine exposure on surfactant gene expression is apparently mediated by nicotinic acetylcholine receptors because it was blocked by D-tubocurarine. The nicotine-induced stimulation of surfactant gene expression could, in part, account for the effect of maternal smoking on the incidence of respiratory distress syndrome.