[Ultrastructural changes in the aortic arch intima in rats with various resistance to emotional stress]

Experiments were performed on 24 male Wistar rats weighing 210 +/- 14 g. Depending on the activity in the open field test, all rats were divided into behaviorally active and passive subgroups. Water-immersion stress (2 hrs) followed by 2-hrs rest period was used as the model of acute emotional stress. Tissue samples from aortic ascending arch were taken from control and stressed rats immediately after decapitation and used for further electron microscopy. The number of micropinocytosis vesicles along the free and basal layers of the cytoplasm and the area of mitochondria were determined. Emotional stress was shown to intensify metabolic processes involving micropinocytosis vesicles between the aortic lumen and its wall. Passive rats display the most severe alterations induced by stress (damages of aortic endotheliocytes, partial regeneration of the plasmalemma by membranes of micropinocytosis vesicles, and decrease in the average area of mitochondria). Morphological equivalents of the initial stages of emotional stress-induced formation of fibrous changes in the aortic arch intima are believed to be found. Such changes can lead to the appearance of atherosclerotic patches.