[The morphofunctional changes in the alveolar epithelium, macrophages and pulmonary surfactant of rats with bleomycin-induced fibrosis].

Interstitial fibrosis was modelled in 100 male rats by means of a single intratracheal administration of bleomycin (0,5 U/100 g of body mass). The stimulation and activation of secretory activity of large (granular) epitheliocytes (alveolocytes of the 2nd type) and alveolar macrophages with maximum alterations were found 3 weeks later, when in the lungs there were numerous foci of interstitial fibrosis. Biochemically, these phenomena were followed by increasing the amount of phospholipids in surfactant (mainly at the expense of phosphatidylcholine) and in membranes of macrophages, which points to interrelation of metabolic processes in the cells, morphologically detected activation of synthesis of surfactant in alveolocytes of the 2nd type and its utilization by alveolar macrophages at the height of the development of bleomycin-induced pneumofibrosis. A supposition has been put forward of a participation of surfactant in the formation of fibrosis.