Resistance vessel structure: effects of treatment.

The purpose of this article is to review the evidence that the resistance vasculature is altered in hypertension, the role that it may play in the pathogenesis of the disease, and the effect of antihypertensive treatment on the abnormalities. In some models of hypertension, functional changes (i.e., increased vascular smooth muscle sensitivity) have been found, but in human essential hypertension, it appears that structural changes in the resistance vasculature predominate. The structural changes result in an increased media:lumen ratio of the resistance vessels, but it is not clear if these changes are also associated with an increased synthesis of vascular wall material, or whether they can alone be due to a remodeling of the vascular wall (i.e., redistribution of existing material). In both essential hypertension and in the spontaneously hypertensive rat, vascular smooth muscle volume appears to be normal, but is increased in renal hypertensive rats, suggesting that hypertrophy may be a response to imposed increases in load. Although there seems to be a close correlation between altered media:lumen ration and blood pressure in all forms of hypertension investigated, it is generally found to be difficult to obtain full regression of vascular structure. The reason for this remains obscure.