Experimental Pulmonary Thromboemboli in Rats after Thoracic X-Irradiation

Abstract

Studies have been made of the intrapulmonic location and the lysis time of blood clots used to produce pulmonary thromboemboli in rats. These studies also demonstrated that normal rats can lyse clots sufficiently large to occlude the lumen of the secondary branches of the pulmonary artery without the production of infarction (1). Other studies have shown that the location and lysis of such clots within the pulmonary artery may be related to the formation of calcified plaques in the wall of the pulmonary artery of the rat (2), comparable to findings in the rabbit (5). For all these studies, animals without known pulmonary pathology were used. A reproducible pulmonic lesion affecting the pulmonary vessels of experimental animals is desired, since pulmonary vascular pathology preceding embolization is considered to be necessary for infarct production (4). X-Irradiation of sufficient energy should produce fairly consistent pathological changes in the pulmonary vessels, for among the most consistent reactions to X-irradiation are morphologic and physiologic changes in the vascular system (5-9). Studies were made therefore to ascertain the effects of varying doses of thoracic X-irradiation on the pulmonary vessels; the response of the X-irradiated animals to experimental pulmonary thrombosis; the ability of these animals to lyse the clots producing thrombosis; and the role of these experimental procedures in the formation of calcified plaques in the wall of the pulmonary artery.