The granulovesicular bodies of the arterial wall.

Small, round, membrane-bound electron-dense bodies were observed in the smooth muscle cells and the intimal and medial intercellular spaces of arteries in the dog, rat, and pig under normal and various experimental conditions. These structures, referred to as granulovesicular bodies (GVB), measured from 0.2 to 0.5 mum. in diameter and contained an inner core of granular and vesicular subunits. The intercellular and extracellular forms of the GVB were structurally similar, and in the interstitial spaces they appeared to have a definite spatial relation to the elements of elastic tissue. The GVB were more numerous under experimental than under normal conditions. It is speculated that the GVB are secretory in nature, originating from the smooth muscle cells, and may play a role in the remodeling of arterial elastic fibers.