In rats that breathed pure oxygen under pressure, their lung cells that make surfactant (type‑II alveolar cells) got swollen, lost surfactant‑producing structures, and the number of these cells dropped. Giving the peptide thymalin (alone or with cytochrome C) helped the cells recover: surfactant‑making bodies grew back, mitochondria returned to normal size, and the cell count went back to healthy levels, especially when both compounds were used together.

The effect of cytochrome C, thymalin and their combination has been studied concerning morphofunctional state of alveolocytes of the II type (A II) in the lungs of 33 non-inbred white rats at the pulmonary form of oxygen poisoning. The phenomenon develops, when the animals are in pure oxygen under pressure of 0.25 MPa for 10 h. The ultrastructural stereological analysis demonstrates that after exposure of the mice in the barochamber, immediately after decompression and during the 1st and the 3d day in the animals not given the pharmacological preparations in the A II diffuse and local edema develops in hyaloplasm, certain changes develop in mitochondria and endoplasmic reticulum. Comparing to intact animals, a relative volume of the lamellar bodies decreases nearly two times, the volume of mitochondria increases by 1.5 times, amount of A II drops. While treating the pulmonary form of oxygen poisoning with cytochrome C or thymalin, in 3 days after beginning to administer the preparations, the relative volume of the lamellar bodies increase by 1.5 times in comparison with those in the group of untreated animals, and at the combined administration-by 2.5 times. This demonstrates stimulation of the pulmonary surfactant synthesis. When the preparations are applied together, by the 3d day the relative volume of mitochondria and amount of A II do not differ from the corresponding indices in intact animals.