Changes of myocardial capillary density in progression of experimental lung emphysema

A morphometrical analysis of changes in the heart of rats with experimental lung emphysema due to single intratracheal administration of papain solution has been done. Special attention has been paid to quantitative changes of capillaries and to the cardiomyocyte diameter in respective regions of the myocardium after one, three and six months following the administration of papain. A histological and morphometrical analysis of changes in the lungs has also been carried out and partial pressures of oxygen and carbon dioxide in the arterial blood of the examined animals have been marked. It has been found that a single administration of papain caused emphysematous changes in the lungs, growing more intense until the third month of the experiment. The progression of these changes corresponded to a capillary density increase in the right ventricle, interventricular septum and in the subendocardial layer of the left ventricle. The increase in the number of capillaries was interpreted as the first adaptive stage of cor pulmonale development and explained by the occurrence of angiogenesis. The changes co-existed with a decrease in partial pressure of oxygen in the arterial blood. After six months of the experiment, a reduction in capillary density in the heart regions mentioned above and a simultaneous increase in the cardiomycyte transversal diameter were observed, being the exponents of evident myocardial hypertrophy. Development of ultrastructural changes in the hearts of rats has been analysed too. Simultaneous development of changes in the right ventricle muscle and in the subendocardial layer of the heart left ventricle myocardium was observed. The role of hypoxia as a one of essential factors responsible for the observed morphologic changes has been discussed.