1987 Volume 54 Issue 2 Pages 184-192_6
The author carried out an ultrastructural investigation into the causative mechanism of pulmo nary fibrosing alveolitis induced by Paraquat administration to the rats on a chronological basis. An attempt was made to correlate the morphological changes with the surfactant activity which was measured by the modified Wilhelmy Balance (Nozaki).
The results obtained are as follows :
1) After Paraquat administration, swelling and degeneration of the type I epithelial cells were observed. The aggregate of fibrin and polymorphonuclear cells was also noted. Then the changes of the osmiophilic bodies of type II epithelial cells were discernible, followed by interstitial edema.
2) In a rather prolonged stage, activated fibroblasts and myofibroblasts increased in number while fibro-collagenous tissue proliferated in alveolar space. Activation of type II epithelial cells and alveolar macrophages was also striking. Intra-luminal narrowing of vasculature, microthrombus formation as well as perivascular fibrosis were also remarkable.
3) The tannic acid stain disclosed the elastic fiber component. The elastic fibers which were basically composed of elastin and elastic microfilaments were undergoing extensive degeneration which was clearly associated with the proliferation of the fibro-collagenous fibers. In this context, the alteration of the elastic component was closely associated with the causative mechanism of pulmonary fibrosis in this particular condition.
4) The alteration of the pulmonary surfactant which was measured by the modified Wilhelmy Balance (Nozaki) disclosed an intimate interrelation between disruption of the alveolar lining layer as well as degeneration and loss of the type II epithelial cells.
5) Thus it is concluded that the pulmonary fibrosing pathology induced by the Paraquat injection may offer a very versatile experimental model to clarify the initial and progressive stages of fibrosis of the lung.
