LEVELS OF PULMONARY SURFACTANT PROTEIN-A IN FETAL LUNG AND AMNIOTIC-FLUID FROM PROTEIN-MALNOURISHED PREGNANT RATS

Surfactant protein A (SP-A) is a major ape-protein of pulmonary surfac tant, which lines the alveolar walls, lowering the surface tension to prevent lung collapse. Pregnant rats were divided into two groups whic h received a diet with either 5% or 20% protein from gestational day 9 . By a sensitive immunoassay, SP-A levels in the fetal lungs and the a mniotic fluid showed a dramatic increase with advancing gestation afte r the initial appearance on gestational day 18 in both diet groups. Si gnificantly lower levels of SP-A in pregnant rats fed 5% protein diet than those in pregnant rats fed 20% protein diet were observed in the fetal lungs on gestational day 21 and in the amniotic fluid on gestati onal days 20 and 21. The profiles of increased SP-A levels in the amni otic fluid reflected those in the fetal lungs during gestation. Immuno histochemical examination with anti-rat SP-A antibody at 21 days of ge station showed that the immunoreactive staining of bronchiolar epithel ial Clara cells and alveolar type II cells were weaker in the fetal lu ng sections from pregnant rats fed 5% protein diet than in those from pregnant rats fed 20% protein diet. It is concluded that protein malnu trition in pregnant rats affects the biosynthesis of SP-A in the fetal lungs, which may have important consequences for prematurity and decr eased respiratory functions in the neonatal lungs at birth.