The entrance of surface active material to pulmonary capillaries in the lungs of newborn rats.

In newborn rats we investigated the entrance of surfactant to the pulmonary capillaries a few minutes after the birth. Time is crucial for the process which can be called "drying" of the lung, when a large amount of intraalveolar fluid enters the pulmonary circulation. Ultrastructural studies have revealed bulk transport and endocytosis of surfactant via alveolar septa to the blood vessels, but it is still questionable whether the entrance of surfactant to pulmonary capillaries is related to its clearance or to "drying" of lung's alveoli.