Aortic smooth muscle cells reaction in rat spontaneous hypertension.

Parallel morphometric, karyometric and ultrastructural studies of the aortic wall in Okamoto-Aoki rats with short term (3-6 months) and long-term (12-16 months) spontaneous hypertension have revealed a progressive thickening of the medial layer, which is associated with an increaase in the mean nuclear area of the arterial medial smooth muscles and reduction in their mean number per unit area. Electron microscopic studies have shown a multiplication of the intracellular components of aortic smooth muscle cells as a base for their enlargement, as well as small single foci of smooth muscle hyperplasia in the area of the innermost interlamellar space in parts of the aortic wall with intimal thickening. Results of these studies allow the conclusion, that hypertrophy is a reaction of arterial smooth muscle cells to an increased mechanical load in hypertension which, in turn, is responsible for the thickening of arterial with Hyperplasia - increase in smooth muscle cells' number in the media - played a subordinate role. The reaction of the aortic wall to elevate blood pressure is interpreted as a manifestation of the normally limited division capacity of smooth muscle cells in mammals, which does not allow an increase in its cellular components. The function of existing arterial smooth muscle smooth cells is enhanced, instead, by hyperplasia of their specific organelles and augmentation of their volume.