Changes in various tissues in the arterial wall of spontaneously hypertensive rats.

1. Using stroke-prone spontaneously hypertensive rats (SHRSP), stroke-resistant spontaneously hypertensive rats (SHRSR) and Wistar-Kyoto rats (WKY), vascular complications and the longevity of rats were investigated. 2. SHRSP aged more than 9.5 months tended to suffer from severe vascular complications such as periarteritis nodosa (PN) of mesenteric artery, while SHRSR very rarely showed severe vascular complications and WKY did not show any complications, because of the different level of systolic blood pressure. 3. Among some tissues PN tended to occur early in the small arteries of the testes and then in mesenteric artery, when these tissues of SHRSP were investigated microscopically. 4. Concerning the influence of systolic blood pressure on arterial smooth muscle layer, the deviation force of this layer was larger in SHRSR compared to WKY (44.7 times in Y axis), which was calculated mathematically and physically using computer analysis. 5. The arterial wall area of PN was enlarged, resulting in the low ratio of lumen/wall. The ratio of arterial lumen/wall was lower in SHRSP when compared to the age-matched WKY. 6. In search for myocardial ischaemia, ECG was recorded. There were positive correlations between PQ interval or SV1 + RV5 and age in the three strains of rats. ST depression more than 1 mm on ECG was most prevalent in old SHRSP, indicating probably the presence of myocardial ischaemia.