ABNORMAL REGIONAL BLOOD-FLOW RESPONSES DURING AND AFTER EXERCISE IN HUMAN SYMPATHETIC DENERVATION

1. Blood pressure, superior mesenteric artery (SMA) and skeletal muscl e blood flow, cardiac index (CI) and systemic vascular resistance resp onses to supine leg exercise were measured in six age-matched normal s ubjects (controls) and in eleven subjects with sympathetic denervation due to primary autonomic failure (AF). 2. During exercise, blood pres sure rose in controls but fell markedly in AP. After exercise, blood p ressure rapidly returned to baseline in controls but remained low in A F. During exercise, systemic vascular resistance fell in controls and AF but tended to fall further in AF and remained low post exercise. CI increased similarly in controls and AF. 3. During exercise, SMA blood flow fell similarly in controls and AF, but the fall initially was sl ower in AF; recovery was more rapid post exercise in controls. SMA vas cular resistance tended to rise less and more slowly in AF and remaine d elevated post exercise. 4. Forearm muscle (FM) blood flow and FM vas cular resistance did not change fi om resting values in controls or BF post exercise. After exercise, leg muscle (LM) blood flow rose and LM vascular resistance fell equally in both groups although LM blood flo w remained elevated, 10 min post exercise in AF. 5. In sympathetically denervated humans, increased blood flow (due to excessive vasodilatat ion, lack of sympathetic restraint, or both) in leg muscle during and after exercise in combination with impaired splanchnic vasoconstrictio n in the early stages of exercise may has-e contributed to exercise-in duced hypotension.