Differences in regional capillary distribution and myocyte sizes in normal and hypertrophic rat hearts.

Data are reported which show significant regional capillary differences in left ventricular endocardium and epicardium of normal rats and of rats with hyperthyroid-induced cardiac hypertrophy. The epicardial region of control rats has 38% more capillaries than the endocardial region. Control endocardial myocytes are 62% larger in cross-sectional area than epicardial myocytes. Hypertrophic hearts exhibit regional differences in capillary density similar to those in the normal hearts, but there is an overall reduction of 12 and 17.5% in capillary density in both regions. The average cross-sectional area of myocytes increases 34.5% in the epicardium and 22.5% in the endocardium.