Role of the vascular factor in hypertension.

A survey is given of experimental results in both man and hypertensive rats, suggesting a rapid and hemodynamically important structural 'resetting' of the systemic precapillary resistance vessels, of the renal 'long-term' and carotid-aortic 'short-term barostats', as well as of the left heart, which together greatly affect both the initiation and maintenance of hypertension. Particularly the adaptation in design of the precapillary resistance vessels, being a per se normal, local response to more sustained changes in transmural pressure ('structural autoregulation'), implies the introduction of a potential vicious circuit once it affects the entire vascular bed. The reason is that this type of altered vessel design leads to a systemic precapillary hyperreactivity that forms a positive feedback interaction with functional excitatory influences as far as their long range, hemodynamic effect on the arterial pressure level is concerned. It is further discussed how various types of structural and functional vascular changes may often coexist, then mutually interacting with each other, and how they may be experimentally separated for detailed analysis.