TUNICA MEDIA REMODELING IN MESENTERIC-ARTERIES OF HYPERTENSIVE RATS

Background: The tunica media of the vascular wall is a composite mater ial comprised of smooth muscle cells and fibrous and nonfibrous matrix proteins. Methods: Using morphometric techniques, this study quantifi es the cell and matrix composition of normotensive (Wistar-Kyoto) and spontaneously hypertensive rat mesenteric arteries. Results: The data show that the superior mesenteric artery (SMA) and small mesenteric ar teries are different in matrix composition, cell-to-matrix ratio, and cellular dense body content. Compared with normotensive arteries, hype rtensive arteries have less basement membrane but more collagen and ex tracellular matrix ground substance. SMA from hypertensive rats has ab out 30% less elastin than does normotensive artery. In contrast, the e lastin content of small arteries of both strains was about the same an d was less than 4% of the matrix area. Except in hypertensive SMA, mem brane dense bodies occupy 7-10% of the cell area and more than 10 time s the area occupied by cytoplasmic dense bodies. In contrast, cells fr om hypertensive SMA have about half the membrane dense body area of th e normotensive cells, A decreased proportion of dense bodies in the hy pertensive SMA is consistent with the ''partial detachment'' of these cells from the matrix. Conclusions: These results are consistent with both cellular and matrix ''remodeling'' in diseased vessels in respons e to continuous, long-term elevated blood pressure. (C) 1996 Wiley-Lis s, Inc.