THE ROLE OF SURFACTANT IN THE STATIC LUNG-MECHANICS OF THE LIZARD CTENOPHORUS-NUCHALIS

We previously showed that the lung of the central Australian lizard. ( Ctenophorus nuchalis, contains a large amount of surfactant, the compo sition of which varies with body temperature. We now show that the spe cific compliance of the lungs of these lizards remains constant regard less of whether they were maintained at 10, 18, 27, 37 or 43-degrees-C for 4 hours. In contrast, the opening pressure was constant up to 27- degrees-C but decreased at 37 and 43-degrees-C. When we lavaged the lu ngs in situ to remove the majority of surfactant, specific compliance decreased while opening pressure increased. The lungs of C. nuchalis a re essentially two bubbles. with the left one larger at low and interm ediate volumes. After collapsing both lungs. the larger left lung alwa ys inflated first. However, following lavage the smaller right lung in flated first. As the larger lung, when collapsed, would have a much gr eater area of epithelial contact, this result is consistent with surfa ctant acting as an 'antiglue'. During deflation the smaller lung colla psed first, consistent with the law of Laplace. Compliance did not cha nge in the saline-filled lung suggesting that the gas-liquid interface does not play a major role. We conclude that in the lungs of these li zards, surfactant is acting as an antiglue. This might be important du ring periods of apnea at low body temperatures, when residual volume i s small and epithelial surfaces may come into contact.