The role of the lymphatics in aiding regression of hypokalemic lesions in rat cardiac muscle

This study describes the role of lymphatics in the removal of macrophages from inflammatory lesions in the heart of hypokalemic rats and rats recovering from hypokalemia. The inflammatory lesions are characterized by focal cardiomyocyte necrosis, edema, and mononuclear infiltrate. The vascular and lymphatic capillaries are maintained along with the basement membrane of the necrotic cardiomyocyte. Through prior investigation, it was revealed that refeeding potassium led to a rapid reduction in lesion area. The purpose of the current investigation was to establish the role of the lymphatics as a means of reducing the lesion area by removal of the cellular infiltrate and edema. Using a limited potassium diet, hypokalemic rats were sacrificed via perfusion fixation during the hypokalemic and the potassium re-supplementation periods. Heart tissue was examined by light and electron microscopy. During the hypokalemic period, phagocytic mononuclear cells were found engulfing necrotic cardiac muscle cells. With refeeding of potassium, these phagocytic cells appeared to be diminished in number, a reduction that coincided with a decrease in the lesion size. Lymphatic channels were dilated and full of mononuclear cells. These channels were differentiated from the vascular capillaries by standard morphological criteria. In conclusion, the lymphatics play an important role in the healing process by reducing the lesion size through the removal of phagocytic cells and the uptake of proteinaceous material.