Age-related alterations in epicardial arteries of spontaneously hypertensive rats.

Proximal portions of the left coronary arteries were examined microscopically in aging female normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). The age-related intimal alterations in SHR were largely limited to endothelial cells, which demonstrated a proliferation of organelles (most notably Weibel-Palade bodies). In the media, degenerative alterations appeared to be most marked near the medio-adventitial junction. Compared to WKY and increasing with age, the media of the SHR epicardial artery demonstrated an accumulation of extracellular elements that included basement membrane-like material, collagen fibers and debris. Complex carbohydrates, as determined with the silver methenamine reaction, were noted to accumulate in a lamellar fashion. Smooth muscle cells demonstrated an age-related tendency (which was exaggerated in SHR) toward development of invaginations and irregular profiles. These observations indicate that age-related structural alterations in epicardial arteries of SHR are progressive, and they support the concept that structural alterations in SHR coronary arteries may represent accelerated aging phenomena.