The pulmonary surfactant is a lipoproteic complex that serves to lower surface tension at the air-liquid interface in the pulmonary alveoli. Approximately 2 to 4% of the pulmonary surfactant is constituted by the protein A (SP-A). The objective of the study was to determine the effects that maternal protein calorie malnutrition has on the fetal pulmonary growth and the production of SP-A messenger RNA in fetal rats.
Materials and methods: Pregnant Sprague Dawley rats were divided into two groups, which received a diet with either 8% or 21% of proteins from gestational day 1 until the day 20. In this last day 11 fetuses were extracted by caesarean section and their lungs were removed to quantify the mRNA of the SP-A. First the mRNA was boosted using the technique of reverse transcriptase and polimerase chain reaction (RT-PCR) and then its concentration was determined by means of fluorodensitometry.
Results: There was a reduction in body weight and in wet lung weights of malnourished fetuses in comparison with the normal fetuses (5.03 +/- 0.20 g vs. 4.32 +/- 0.32 g, p < 0.05 and 79.0 +/- 3.8 mg vs. 146.0 +/- 3.4 mg, p < 0.05, respectively). The densitometric analysis of the SP-A mRNA concentration demonstrated a reduction of 32% in the malnourished fetuses (0.52 +/- 0.11 vs. 0.77 +/- 0.07, p < 0.05) compared with the normal fetuses.
Conclusions: The maternal protein calorie malnutrition affected the pulmonary development and the synthesis of the SP-A mRNA. These data suggest that a defect occurrs at pre-transcriptional level that results in a diminution of the concentration of mRNA of SP-A in the neumocytes type II.