Pulmonary surfactants and their role in pathophysiology of lung disorders.

Surfactant is an agent that decreases the surface tension between two media. The surface tension between gaseous-aqueous interphase in the lungs is decreased by the presence of a thin layer of fluid known as pulmonary surfactant. The pulmonary surfactant is produced by the alveolar type-II (AT-II) cells of the lungs. It is essential for efficient exchange of gases and for maintaining the structural integrity of alveoli. Surfactant is a secretory product, composed of lipids and proteins. Phosphatidylcholine and phosphatidylglycerol are the major lipid constituents and SP-A, SP-B, SP-C, SP-D are four types of surfactant associated proteins. The lipid and protein components are synthesized separately and are packaged into the lamellar bodies in the AT-II cells. Lamellar bodies are the main organelle for the synthesis and metabolism of surfactants. The synthesis, secretion and recycling of the surfactant lipids and proteins is regulated by complex genetic and metabolic mechanisms. The lipid-protein interaction is very important for the structural organization of surfactant monolayer and its functioning. Alterations in surfactant homeostasis or biophysical properties can result in surfactant insufficiency which may be responsible for diseases like respiratory distress syndrome, lung proteinosis, interstitial lung diseases and chronic lung diseases. The biochemical, physiological, developmental and clinical aspects of pulmonary surfactant are presented in this article to understand the pathophysiological mechanisms of these diseases.

Densidad óptica a 650 nm y fosfatidilglicerol en la evaluación de la inmadurez pulmonar fetal / Optic density of 650 nm and phosphatydilglycerol in the fetal lung inmaturity evaluation

Se estudió el valor de la lectura de la densidad óptica a 650 mm (DO650) para predecir la presencia o ausencia de fosfatidilglicerol (PG) en 52 muestras de LA no contaminadas con sangre ni meconio, obtenidas por amniocentesis transabdominal, en las cuales la prueba de Clements (PC) fue informada como negativa. La totalidad de las muestras excepto una tuvieron lectura de DO650 * 0,050, detectándose la presencia de PG en 22 de ellas (42,3%), no observándose diferencias significativas en ningún rango de lectura. Nuestros resultados demuestran que la DO650 no permite discriminar la presencia o ausencia de PG en muestras de LA con PC negativa, lo puede ser debido a que las bajas concentraciones necesarias para detectar PG en LA son incapaces de modificar significativamente la DO650. Se concluye que cuando la PC es negativa, la lectura de la DO650 es un paso innecesario en la evaluación de la inmadurez pulmonar fetal