Spatial relationship between cardiac mast cells and coronary capillaries in neonatal rats with cardiomegaly

Density of cardiac mast cells and their localization with respect to coronary capillaries was studied in two experimental situations. First, cardiac hypertrophy produced by aortic constriction in 5-day-old rats was studied. Left ventricular weight increased more than twofold in this experimental situation, while the increases in total capillary length and total number of cardiac mast cells were much smaller, resulting in decreased densities of both tissue components. In the second series of experiments, localization of cardiac mast cells at two distinct portions of coronary capillaries was studied in normal hearts of adult rats. Differential histochemical staining enabled us to distinguish between the portions of capillaries close to arterioles and portions on the venular side. The number of mast cells close to arteriolar portions of coronary capillaries was significantly higher than one would expect in the case of their even distribution along the capillary wall. The relationship between the mast cells and formation of new capillaries is discussed.