A new simple method of staining exogenous surfactant in experimental research

Two commonly used techniques in experimental lung research have helped to d etermine which variables influence surfactant distribution within the lung: radioactive labelling of surfactant components and admixture of coloured m icrospheres to surfactant. However, neither technique allows the descriptio n of surfactant distribution at the alveolar level. The aim of this study w as to establish a new technique using histology colourants for admixture to exogenous surfactant to make exogenous surfactant visible by light microsc opy. In a step by step approach the authors evaluated the properties of a variet y of green colourants when added to a natural porcine surfactant preparatio n for their ability to homogeneously mix with surfactant, to bind to surfac tant to adhere to a glass slide, to not be "overstained" by standard haemat oxylin-eosin and Elastica van Giesson staining, to not influence in vitro s urface tension properties of surfactant using a Wilhelmy balance, to not in fluence oxygenation and ventilation in a lung-lavage rat model and to prese rve their colour and adherence to exogenous surfactant on lung specimens vi sualized by light microscopy. Only one of the tested green histology colourants (Green Dye(R)) fulfilled all requirements and showed a brilliant green colour in a distribution patt ern typical of surfactant at the alveolar level. It is concluded that the a uthors have established a new, simple and inexpensive method of staining ex ogenous surfactant for evaluation of its distribution by light microscopy a t the alveolar level.