Cell size and capillary supply of the hypertensive rat heart: quantitative study.

Cardiac mass, cell size and capillary supply were studied in the hearts of spontaneously hypertensive rats (SHR) and compared to genetically similar non-hypertensive Wistar-Kyoto (WKY) of three adult ages: 5, 15 and 23 months. The left ventricular weight of SHR was not significantly greater than that of WKY at 5 months, but was by 15 months and became even more so by 23 months. This increase could be attributed to hypertrophy of the individual cardiac muscle cells and therefore, the estimated total number of myocytes per left ventricle was essentially the same in all experimental groups. Various indices of the myocardial capillary supply were also investigated. Cardiac hypertrophy in older hypertensive rats was characterized by greater and more variable intercapillary spacing, which may have importance in myocardial oxygen supply.