The aim of this study was to characterize the presence of type II pneumocyte and the beginning of the surfactant protein production in bovines to the correlated gestational age. Lungs of fetuses at 4 months gestational age were found to be in the canalicular development phase, without presence of type II pneumocytes or appearance of electrophoretic bands compatible with the presence of the surfactant protein. In fetuses at 5 months of gestational age, the lungs were at the terminal sac phase, with the presence of primitive alveolus, formed by cubical epithelium and areas formed by pneumocytes I and pneumocytes II. No electrophoretic bands compatible to the surfactants proteins were identified. In contrast, lungs of fetuses at 6 months of gestational age showed, development of terminal sac phase, with the presence of type I and type II pneumocytes. In this phase, proteic determination for the SDS - PAGE analysis showed the presence of bands between 26 to 36kDa, demonstrating SP - A production, which is the surfactant protein found in highest amount. From the 7th gestational month on, the phase of terminal sac is more evident and complex, with intense sprouting vascularization. The type I pneumocyte had a more squamous aspect and type II pneumocyte were more globular. In the SDS - PAGE analysis of the bronchial - alveolar wash, surfactant protein bands had been observed with a profile similar to that of the newborn animals. In newborn animals, lungs in alveolar phase showed the development of type I and II pneumocytes. The profile of the bronchial - alveolar wash from the newborn was similar to an adult animal, presenting the same bands in triplets. These results suggest that early born fetuses, from 7 months of pregnancy could have a guarantee of surviving due to possible functionality of respiratory system because the lung presented all necessary features for surphactant protein syntheses. However, new clinical studies related to respiratory system functionality open new venues for newborn bovine's experiments respiratory physiology.
type II pneumocyte; lung; surfactant protein; bovine
