| Abstract: | Pilocarpine HCl, a parasympathomimetic drug, was administered to pregnant white rabbits in a daily subcutaneous injection of 5 mg/kg on days 24 through 27 of gestation. Fetuses from these animals and from salineinjected controls were obtained by caesarean section at day 28 of gestation. Light microscopic examination revealed thinner alveolar septa in the lungs of pilocarpine-treated fetuses and, morphometrically, a significant increase in the number of mature type II cells, both per unit area and per 1,000 lung cells of any kind. Examination by electron microscopy revealed that the alveolar epithelium of pilocarpine-treated fetuses demonstrated morphologic correlates of increased maturation. These included thinning of type I cells to form blood-air barriers and substantial reductions in the glycogen content of both epithelial cell types. Type II cells of pilocarpine-treated fetuses contained (as indicated by morphometric analysis) more and larger lamellar inclusion bodies, as well as more multivesicular bodies than those of controls. Biochemical determination indicated that the glycogen content of fetal lung, but not liver, was reduced significantly in the pilocarpine-treated group. The findings of this study indicate that maternal administration of pilocarpine results in increased maturation of the fetal alveolar epithelium, thus providing a basis for the autonomic manipulation of fetal lung maturation. |
