Ultrastructural Studies on Arteriolar Lesions in Experimental Hypertension

With the use of four different experimental hypertension groups (Goldblatt's renal hypertension, adrenal regeneration hypertension, steroid induced hypertension, salt treated hypertension) of rats, electron microscopic observation was carried out on the morphogenesis of hypertensive vascular lesion. There are two representative patterns of vascular lesion due to hypertension at the early stage. They both appear in medial smooth muscle cells. One of them is focal cytoplasmic necrosis of smooth muscle cells which can be seen from the early stage of hypertension. The medial lesion secondarilly induces fibrin deposition resulting in ‘fibrinoid necrosis’. The other change is ‘moth-eaten structure’ which is seen mostly in the cases affected by long-term hypertension, which irregular foveation of muscle cell and accumulation of granules and vesicles in the intercellular matrix, and which being accompanied with focal cytoplasmic necrosis may be progressed into fibrous thickening or hyaline thickening. Focal cytoplasmic necrosis which is the initial change towards fibrinoid necrosis seems to be caused by toxic chemical factors rather than by biophysical factors of hypertension. In some advanced fibrinoid necrosis, endothelial cells are transmitted to the media through the fenestra of internal elastic lamella and perform phagocytosis of the materials accumulated there. There was no qualitative difference in vascular change among the four different experimental hypertension groups.