CHARACTERISTICS OF SURFACTANT FROM SP-A-DEFICIENT MICE

Mice that are surfactant protein (SP) A deficient [SP-A(-/-)] have no apparent abnormalities in lung function. To understand the contributio ns of SP-A to surfactant, the biophysical properties and functional ch aracteristics of surfactant from normal [SP-A(+/+)] and SP-A(-/-) mice were evaluated. SP-A-deficient surfactant had a lower buoyant density , a lower percentage of large-aggregate forms, an increased rate of co nversion from large-aggregate to small-aggregate forms with surface ar ea cycling, increased sensitivity to inhibition of minimum surface ten sion by plasma protein, and no tubular myelin by electron microscopy. Nevertheless, large-aggregate surfactants from SP-A(-/-) and SP-A(+/+) mice had similar adsorption rates and improved the lung volume of sur factant-deficient preterm rabbits similarly. Pulmonary edema and death caused by N-nitroso-N-methylurethane-induced lung injury were not dif ferent in SP-A(-/-) and SP-A(+/+) mice. The clearance of I-125-labeled SP-A from lungs of SP-A(-/-) mice was slightly slower than from SP-A( +/+) mice. Although the absence of SP-A changed the structure and in v itro properties of surfactant, the in vivo function of surfactant in S P-A(-/-) mice was not changed under the conditions of these experiment s.