RUPTURE OF THE INTERNAL ELASTIC LAMINA AND VASCULAR FRAGILITY IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS

We studied a possible relation between stroke and an enhanced susceptibility to rupture of the arterial internal elastic lamina by comparing stroke-prone spontaneously hypertensive rats with spontaneously hypertensive rats, which have a very low incidence of stroke. We quantified interruptions in the internal elastic lamina in certain arteries and studied the effect of beta-aminopropionitrile, an inhibitor of cross-link formation in collagen and elastic fibers, on rupture of the internal elastic lamina and on mortality in these two substrains. To eliminate any influence of higher blood pressure in the stroke-prone rats on the parameters studied, we used antihypertensive treatment to obtain equivalent blood pressures in the two substrains. Results showed that stroke sensitivity was associated with an enhanced early spontaneous rupture of the internal elastic lamina in the caudal artery, an increased susceptibility to beta-aminopropionitrile-induced rupture of the internal elastic lamina, and earlier mortality, mainly from aortic rupture, under beta-aminopropionitrile treatment. These findings suggest that stroke-prone rats have an enhanced minor connective tissue defect that is expressed by rupture of the internal elastic lamina and may be related, at least in part, to their greater vascular fragility and increased susceptibility to stroke.