Fenestrations of the carotid internal elastic lamina and structural adaptation in stroke-prone spontaneously hypertensive rats

Our aim was to determine the structural factors that determine the mechanic al adaptation of the carotid arterial wall in stroke-prone hypertensive rat s (SHRSP). Distensibility-pressure and elastic modulus-stress curves assess ed by in vivo echo-tracking measurements indicated a reduction in arterial stiffness in 13-week-old SHRSP compared with Wistar-Kyoto rats (WKY). Elast in and collagen contents determined biochemically were not different betwee n SHRSP and WKY. Confocal microscopy showed that the mean area of fenestrat ions and fraction of area occupied by fenestrations of the internal elastic lamina (IEL) were smaller in SHRSP than in WKY, which indicated a reductio n in stress-concentration effects within the IEL. Immunohistologic staining of EIIIA fibronectin isoform and total fibronectin (also as determined by Western blot) was greater in SHRSP, which suggested increased cell-matrix i nteractions. We suggest that these structural modifications of the vascular wall play a synergistic role in the mechanical adaptation to a high level of stress in SHRSP.