NATURAL SURFACTANT AND HYPEROXIC LUNG INJURY IN PRIMATES .2. MORPHOMETRIC ANALYSES

Natural surfactant and hyperoxic lung injury in primates. II. Morphome tric analyses. J. Appl. Physiol. 76(3): 1002-1010, 1994. - Diffuse lun g injury is accompanied by low compliance and hypoxemia with histologi cal evidence of endothelial and alveolar epithelial cell disruption. T he histological effects of treatment of an acute diffuse lung injury w ith a natural surfactant product were evaluated in a primate model bec ause surfactant function and content have been shown to be abnormal in diffuse lung injury in both animals and humans. Ten baboons were vent ilated with 100% O-2 for 96 h, and 5 were given an aerosol of natural porcine surfactant. Physiological and biochemical measurements of the effects of hyperoxia and surfactant treatment are presented in a compa nion paper. After O-2 exposure, lungs were fixed and processed for qua ntitative electron microscopy. The responses to O-2 included epithelia l and endothelial cell injuries, interstitial edema, and inflammation. The hyperoxic animals treated with surfactant were compared with the untreated animals; the treatments altered neutrophil distribution, fib roblast proliferation, and changes in the volumes of type I epithelial cells and endothelial cells. Surfactant-treated animals also had decr eased lamellar body volume density in type II epithelial cells and pre servation of endothelial cell integrity. These changes suggest complex effects of natural surfactant on the pulmonary response to hyperoxia, including protection against epithelial and endothelial cell destruct ion as well as significant interstitial inflammation and fibroblast pr oliferation. We conclude that natural surfactant treatment of hyperoxi c lung injury in primates resulted in partial protection of epithelial and endothelial cells but also increased the accumulation of fibrobla sts in the lung.