Physicochemical Investigation on the Pulmonary Surfactant of Some Vertebrates

Large aggregate (LA) fraction of the pulmonary surfactant (PS) isolated from five different animals of the vertebrate group, lungfish, chicken, crocodile, stumpie lizard and guinea pig were isolated and characterized. Active pulmonary surfactant components were obtained by chloroform-methanol extraction of the saline suspended LA fraction. Total phospholipid (PL) and protein content were estimated biochemically by standard enzymatic methods. A systematic progression in the PL and protein content was noticed with the developmental sequence of the animals, except the crocodile, which could be due to the difficulty in the PS isolation procedure. In vitro functionality of the solvent spread film was carried out in a Langmuir surface balance by way of surface pressure (π)-area (A) measurements. PS from all the species exhibited reversible compression and expansion cycles. A clear correlation between the maximum attainable surface pressure (π_max), also known as the collapse pressure (π_c) and the developmental sequence, with some exceptions, could have been established. Langmuir-Blodgett deposits, transferred onto freshly cleaved mica, were imaged by atomic force microscopy for the five different species. DPPC enriched domains showed different dimensions for the five different species. The comprehensive set of studies shed light on the composition, film functionality and structure of the pulmonary surfactants of the vertebrates where a correlation with the evolution sequence is observed.