effects of maternal nicotine exposure on expression of collagen type iv and its roles on pulmonary bronchogenesis and alveolarization in newborn mice

nicotine is one the chemical substance with high level of toxically. it crosses the placenta and accumulates in the developing organs of fetus. our previous investigations indicated that collagen type iv plays a key role in basement membrane of various embryonic organs. in this study we evaluated the effect of maternal nicotine exposure pre and postnatal period on collagen iv expression during bronchogenesis and alveolarization in the lungs of newborn mice. female balb/c mice were mated and sperm positive in vaginal smear was designated as embryonic day zero. pregnant mice were divided into 2 experimental and 2 control groups. experimental group 1, received 3 mg/kg nicotine intrapritoneally from day 5 of gestation to last day of pregnancy. experimental group 2 received the same amount of nicotine during the same gestational days as well as 2 first week after birth (lactation). the control groups received the same volume of normal saline during the same periods. at the end of exposure times, all of newborns were anesthetized and their lungs were removed for immunohistochemical method. our finding indicated that collagen reaction in the bronchial basement membrane and extra cellular matrix of lung parenchyma in experimental groups increased significantly compared to control groups. our results also showed alveolar remodeling and abnormal bronchogenesis were observed in experimental group especially group 2. these data indicate that maternal nicotine exposure may induce abnormal collagen iv expression and cause defects in bronchopulmonary development.