Remodeling of Cerebral Arterioles in Chronic Hypertension

Chronic hypertension impairs dilatation of cerebral arterioles. Impairment of dilatation generally has been attributed to hypertrophy of the vessel wall with encroachment on the vascular lumen. In this study, we tested the hypothesis that a reduction in external diameter may contribute to encroachment on the vascular lumen during chronic hypertension. We examined 10–12-month-old, anesthetized Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP). External diameter, stress, and strain of pial arterioles were calculated from measurements of pial arteriolar pressure (servo null), diameter, and crosssectional area of the arteriolar wall. During maximal dilatation produced with ethylenediaminetetraacetic acid, cross-sectional area of the arteriolar wall was greater in SHRSP than in WKY rats (2,038±57 vs. 1,456±61 μm2, p < 0.05). External, as well as internal, diameter was less in SHRSP than in WKY rats (101+3 and 88±3 /tm in SHRSP vs. 111±3 and 102±3 fim in WKY rats for external and internal diameter, respectively, p < 0.05). Reduction in external diameter accounted for 76% of encroachment on the lumen in SHRSP, and hypertrophy per se accounted for only 24%. Distensibility of deactivated pial arterioles was increased in SHRSP. These findings suggest that reduction in external diameter plays an important role in impairment of maximal dilatation of cerebral arterioles in SHRSP, and reduction in vascular diameter in SHRSP cannot be accounted for by altered distensibility. We propose that, during chronic hypertension, cerebral arterioles undergo structural remodeling that results in a smaller external diameter and encroachment on the vascular lumen. Reduction in external diameter appears to account for most of the impairment of cerebral vasodilatation that occurs in chronic hypertension.

[1]  H. Bohlen,et al.  Microvascular adaptation in the cerebral cortex of adult spontaneously hypertensive rats. , 1984, Hypertension.

[2]  M. Miyazaki,et al.  Length-passive tension relationships in cerebral and peripheral arteries isolated from spontaneously hypertensive and normotensive rats. , 1982, Japanese circulation journal.

[3]  C. Nordborg,et al.  The morphometry of consecutive segments in cerebral arteries of normotensive and spontaneously hypertensive rats. , 1985, Stroke.

[4]  M. Hart,et al.  Mechanics of Cerebral Arterioles in Hypertensive Rats , 1988, Circulation research.

[5]  W. Halpern,et al.  Biochemical and mechanical properties of resistance arteries from normotensive and hypertensive rats. , 1983, Hypertension.

[6]  B. Folkow,et al.  Background of increased flow resistance and vascular reactivity in spontaneously hypertensive rats. , 1970, Acta physiologica Scandinavica.

[7]  B. Johansson,et al.  Cerebral Vasomotor Reactivity in Normotensive and Spontaneously Hypertensive Rats , 1979, Stroke.

[8]  C. Nordborg,et al.  Morphometric Study on Cerebral Vessels In Spontaneously Hypertensive Rats , 1980, Stroke.

[9]  S. Ibayashi,et al.  Autoregulation of cerebral blood flow in young and aged spontaneously hypertensive rats (SHR). , 1984, Gerontology.

[10]  D. Short The vascular fault in chronic hypertension with particular reference to the role of medial hypertrophy. , 1966, Lancet.

[11]  D. Heistad,et al.  Mechanisms of protection against stroke in stroke-prone spontaneously hypertensive rats. , 1983, The American journal of physiology.

[12]  D. Bohr,et al.  Structural and functional changes in cerebral arteries from spontaneously hypertensive rats. , 1983, Hypertension.

[13]  M. Hart,et al.  Composition and mechanics of cerebral arterioles in hypertensive rats. , 1988, The American journal of pathology.

[14]  M. Brody,et al.  Effect of Chronic Hypertension and Sympathetic Denervation on Wall/Lumen Ratio of Cerebral Vessels , 1980, Hypertension.

[15]  D. S. Short,et al.  The arteries of the small intestine in systemic hypertension. , 1959, The Journal of pathology and bacteriology.