Arterial Responses to Compromised Blood Flow*

Chronic decreases in arterial blood flow rates elicit arterial constriction followed by remodeling of the artery wall that entrenches a reduced internal diameter. This adaptive response may provide an important compensatory adaptation to physiological reductions in blood flow, but it may also exacerbate pathologic disorders that compromise tissue perfusion. A capacity to manipulate this response requires a knowledge of the mechanisms that control it. Our studies have shown that the response is endothelium-dependent, and that it is probably initiated by release of a vasoconstrictor. This finding suggests that endothelium-derived agonist(s) are involved. We assessed the potential role of prostanoids, endothelin, and a local vessel wall renin-angiotensin system. All of these assessments yielded negative results. It appears, therefore, that a novel vasoactive substance initiates the adaptive response of arteries to reduced blood flow.