AGING-AND HYPERTENSION-ASSOCIATED CHANGES OF MEDIAL SMOOTH MUSCLE CELLS OF THE LATERAL STRIATE ARTERIES

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Histometric and histological studies were made on aging-and hypertension-associated changes in the lateral striate arteries from 88 autopsy cases, including 34 normotensive cases, aged 9 fetal months to 72 years, 20 hypertensive cases, aged 23 to 80 years, and 34 others, with the following results : 1. In the lateral striate arteries of normotensive cases, smooth muscle cell counts per unit areas of the media decreased with aging while the interstitial tissue increased. The decrease in smooth muscle cells resulted from their necrosis.2. Medial smooth muscle cell counts in the arteries were smaller in hypertensives than in normotensives of the corresponding age, and the difference between them became greater with age. The necrosis and disappearance of the medial smooth muscle cells were most remarkable in aged hypertensive cases.3. In old normotensive or hypertensive cases, the necrosis and disapperance of the medial muscle cells resulted in interstitial widening, where fine granular substance derived from necrotic muscle cells, PAS-positive basement membrane-like substance and collagen fibers were increased. These changes were more intensive in hypertensive cases than in old ones.4. Medial muscle cell counts in the putaminal segment of the lateral striate arteries of hypertensive cases with intracerebral microaneurysms were smaller by 20-40% than those in hypertensive cases without the aneurysms.5. The cross-section areas and external diameters at various sites of the lateral striate arteries were greater in hypertensives than in normotensives, and the differences between them were greater in old cases.6. In the lateral striate arteries of hypertensive cases, cellulofibrous intimal thickening, swelling and duplication of the internal elastic lamina, and blood plasma and foam cell infiltration of the intima were observed from the third decade, and their frequencies and intensities increased with age.