PERINATAL LUNG DEVELOPMENT FOLLOWING MATERNAL EXPOSURE TO METHYLMERCURIC CHLORIDE

Mercury ingested from dietary sources has potent neurotoxic and terato genic effects. Initial studies have shown that mercury may also affect fetal lung development. Since these pulmonary effects may play a role in subsequent neonatal morbidity and mortality due to compromising of the development of the lung, mercury effects in fetal and neonatal lu ng were investigated. Methylmercuric chloride (MMC), 1,000 ppm (15 mg/ kg of body weight), was administered via an intragastric tube to timed -pregnant Swiss/Webster mice on day 9 of gestation. Lungs from fetuses on gestational day 18 and from neonates on days 1, 5, or 10 after bir th were studied. Significant changes in MMC-exposed lungs compared to controls occurred at postnatal day 1. At this time, lung weight per gr am body weight increased, phospholipid content per gram of lung or per microgram of DNA decreased, while DNA per gram of lung increased. Met hylmercury appears to have delayed lung maturation. Cuboidal epithelia l cells in alveolar tubules contained conspicuous glycogen deposits, a nd differentiation of alveolar type II cells was adversely affected. T hese results suggest that prenatal exposure to methylmercury may be de trimental to lung development, specifically to the initiation of surfa ctant synthesis, by delaying the normal pattern of maturation of the a lveolar type II cells within the lungs. (C) 1994 Wiley-Liss, Inc.