EFFECTS OF ENVIRONMENTAL TOBACCO-SMOKE EXPOSURE IN-UTERO AND OR POSTNATALLY ON BRAIN-DEVELOPMENT/

We evaluated whether environmental tobacco smoke exposure in utero and /or postnatally affects the biochemical composition of the brain. Preg nant Sprague-Dawley rats were exposed to filtered air (FA) or to sides tream smoke (SS) for 4 h/d, 7 d/wk from d 3 of pregnancy until deliver y, then their female pups were exposed to either FA or SS for 9 wk pos tnatally. This resulted in four exposure conditions: in utero FA follo wed by postnatal FA (FA/FA), in utero FA followed by postnatal SS (FA/ SS), in utero SS followed by postnatal FA (SS/FA), and in utero SS fol lowed by postnatal SS (SS/SS). After completion of the exposures, the brains were removed and divided at the pontomesencephalic junction int o forebrain and hindbrain; each specimen was then analyzed for DNA, pr otein, and cholesterol concentration. Data were analyzed by 2-way anal ysis of variance. In utero SS had no effect on these three biochemical measurements. However, postnatal SS reduced hindbrain DNA concentrati on (an indicator of cellular density) by 4.4% (p = 0.001). In addition , the hindbrain protein/DNA ratio (an index of cell size) was increase d in these animals by 8.4% (p = 0.001). Hindbrain weight was not affec ted by SS exposure, but body weight was reduced by 6.4% (p = 0.016). T hese data suggest that postnatal exposure to SS affects the hindbrain (a region which undergoes significant postnatal growth) by reducing th e total number of cells and by increasing cell size. Hindbrain cellula r hypertrophy may help offset the decrease in cell number, thereby lea ving hindbrain weight unchanged. Despite preserved hindbrain weight, t hese effects of postnatal exposure to SS may result in neurologic dysf unction.