Morphometric studies on retinal microangiopathy and myocardiopathy in hypertensive rats (SHR) with induced diabetes.

In experiments of 4 and 8 months duration, blood pressure (BP) and heart rate (HR) were measured periodically in streptozotocin-diabetic (D) rats of normotensive (WKY) and hypertensive (SHR) strains and in corresponding controls (C). BP and HR of D were lower than those of C. In both experiments body length, heart weight and the heart weight/body length ratio (W/L) of D were reduced at autopsy. The number of myocardial cell nuclei per test area was increased in D, indicating a reduced myocardial cell size. No specific change was found at any time in the coronary arteries of rats from any of the groups examined. At 4 months, the retinal capillary basement membrane (BM) of the SHR strain was significantly thicker than that of the WKY strain. At 8 months the BM of D rats was significantly thicker than that of C, but there was no difference between strains. Our results demonstrate that long-term diabetes promotes BM thickening in both normotensive and hypertensive animals. Hypertension does not seem to potentiate diabetes in inducing microangiopathy. Diabetes, however, by causing a lower heart weight and by reducing the heart rate may influence negatively the development of hypertension in the SHR strain. It also appears that there is no direct relationship between increased retinal capillary BM thickness and myocardiopathy.