AN IMMUNOHISTOCHEMICAL STUDY OF THE EXPRESSION OF SURFACTANT APOPROTEIN IN THE HYPOPLASTIC LUNG OF RABBIT FETUSES INDUCED BY OLIGOHYDRAMNIOS

We shunted amniotic fluid from alternate gestational sacs into the mat ernal peritoneal cavity between 23 and 30 days gestation in fetal rabb its (full term, 31 days) to investigate the effect of oligohydramnios on surfactant apoprotein A (SP-A) expression by an immunohistochemical morphometric analysis. The amniotic shunt produced a significant decr ease in the amniotic fluid volume (P < 0.02), as well as a reduction i n the lung weight (P < 0.005) and lung/body weight ratio (P < 0.001), which indicated lung hypoplasia. These fetuses also showed a statistic ally significant reduction of SP-A expression, ie, SP-A-positive type II cells per unit area (P < 0.05), SP-A-positive type II cells/total c ells ratio (P < 0.001), the percentage of SP-A-positive area per unit area (P < 0.005), and the SP-A-positive area/alveolar epithelium area plus the lung interstitium area ratio (P < 0.005). These results sugge st that oligohydramnios significantly retards and modifies the structu ral growth and functional development of alveolar type II cells in SP- A expression. This animal model of hypoplastic lung in fetuses is thus considered to be useful in helping to further develop the treatment f or hypoplastic lung.