Disparate Mechanical and Functional Properties of Spontaneously Hypertensive Rat and Spontaneously Hypertensive Heart Failure Rat Penetrating Arterioles

Hypertension is associated with significant changes in the vascular system and is an important risk factor for cerebrovascular disease. Moreover, hypertension is a dominant determinant of heart failure, and both contribute to the development of cognitive decline and dementia. Despite these links, there is limited understanding of how hypertension and risk of heart failure influence the structure, function, and mechanical properties of cerebral arterioles. We examined the effects of hypertension, alone or with predisposition for heart failure, on penetrating arterioles. Using arterioles isolated from rats with genetic hypertension, structural properties, mechanical behavior, and functional responses were characterized by pressure myography. Penetrating arterioles from spontaneously hypertensive heart failure (SHHF) rats exhibited eutrophic remodeling, reduced compliance, and increased stiffness. In contrast, penetrating arterioles from spontaneously hypertensive rats (SHR) were more compliant and less stiff despite similar structural remodeling. Increased collagen deposition in SHHF arterioles was consistent with reduced compliance, whereas SHR arterioles had unchanged collagen-elastin ratio. SHHF and SHR arterioles were functionally different when exposed to pharmacologic mediators of vasomotor response. After exposure to endothelial N-methyl- d -aspartate receptor coagonists, glutamate and d -serine, vasorelaxation was reduced in SHHF rats but not in SHR relative to normotensive controls. In contrast, acetylcholine-induced vasorelaxation was maintained in SHHF rats but enhanced in SHR. Furthermore, sodium nitroprusside caused vasorelaxation in normotensive arterioles, whereas vasoconstriction was observed in both hypertensive strains. Therefore, penetrating arterioles undergo compensatory adaptations in hypertension, but not when there is a genetic propensity for developing heart failure.