Localization of vascular resistance changes during hypertension.

Aincrease in the vascular resistance of virtually every organ system is a wellknown characteristic of hypertension, as modeled by spontaneously hypertensive rats (SHR) and renovascular hypertensive rats. However, the most important issue may be where in the macrovasculature and microvasculature of a given organ the greatest increase in resistance occurs. The relevance of this issue can be considered from two perspectives. First, if a limited region of the vasculature in each organ is responsible for the bulk of the increased resistance, determining which region is predominantly involved would allow definitive evaluation of the abnormal morphological and behavioral characteristics. Second, if the overall arterial vasculature is relatively uniformly involved in elevating the vascular resistance, a general cellular or control system abnormality of the vessel wall potentially can be identified. In effect, the question to be answered is whether an isolated or generalized vascular problem contributes to the development and maintenance of hypertension.