Modulation of pulmonary bombesin by nicotine and vagotomy

In pregnant hamsters, three transplacental injections of the ganglionic agonist nicotine resulted in a dose-dependent decrease in the concentration of mammalian bombesin (MB) in the lungs of neonatal (1 day old) animals. This decrease in neonatal MB did not occur if nicotine was given only once during gestation, or when it was given three times in conjunction with the ganglionic antagonist mecamylamine. In one week old animals born of mothers who had been exposed to three doses of nicotine during gestation, lung MB had returned to control levels. When nicotine was injected into neonatal animals, lung MB acutely increased. Right sided vagotomy to young hamsters resulted in an increase in the ratio of lung MB (right vs. left lobe) 1 week after surgery. Administration of nicotine to vagotomized animals resulted in decreased total lung MB and normalization of the MB ratio. Thus, nicotine has a potent modulatory influence on lung MB during fetal and neonatal development and maturation. This influence is also present in young animals that are subjected to partial denervation. Our hypothesis is that the innervation of pulmonary neuroendocrine (PNE) cells influences both PNE cell growth and its synthetic function. PNE MB, which is an epithelial and neoplastic growth factor, may play a role in this response.