[Experimental study of the effect of cobalt irradiation on the rabbit lung].

Rabbit lungs were irradiated with a unique dose of 3,150 rads of CO60. The time related study (from the end of irradiation to 28 days after-wards) of the ultrastructural changes in the alveolo-capillary membrane, shows that the early lesions involve first of all the endothelium, then the epithelium and the surfactant, interstitial involvement being the latest. The course of the lesions is maximal on the 7th day, while interstitial involvement appears and is amplified in the three following weeks, whereas cellular involvement completely regresses. Qualitative study of phospholipids from the pulmonary washing fluid of the irradiated lung shows early changes in the composition of surfactant (fall in lecithins and appearance of substances with similar structure) then a return to a practically normal composition around the 21st day. The nature of this early change in surfactant is debated: is it a change in surfactant secreted and/or an early change in the process of synthesis of surfactant?