METABOLIC AND VASCULAR EFFECTS OF CIRCULATING ENDOTHELIN-1 DURING MODERATELY HEAVY PROLONGED EXERCISE

The aims were to investigate 1) the effects of endothelin-1 (ET-1) dur ing exercise and 2) the influence of exercise on arterial ET-1 levels. Six healthy subjects performed two exercises of 2 h duration at 50% o f peak oxygen uptake preceded by intravenous infusion of physiological saline or ET-1 (4 pmol . kg(-1) . min(-1)). Blood specimens were take n from arterial and hepatic vein catheters. Arterial ET-1 rose 15-fold during the infusion. Splanchnic blood flow fell after ET-1 and remain ed lower than in control subjects during exercise (P < 0.001). Splanch nic glucose production was similar to 25% lower compared with control values during the whole exercise period (P < 0.01). Neither heart rate , arterial glucagon, insulin, catecholamines, renin, glucose, lactate, nor glycerol levels differed from control exercise values. The calcul ated gluconeogenesis from glycerol and lactate did not differ from the control values. ET-1 levels rose approximately twofold in the control exercise (P < 0.01) and in another group of seven subjects performing 1 h of exercise at 70% of peak oxygen uptake (P < 0.001). In conclusi on, ET-1 levels increased during exercise without ET-1 administration. In addition, circulating ET-1 has a (direct or indirect) regulatory a ction on splanchnic blood flow and glucose metabolism during exercise (and possibly under pathophysiological conditions) in humans.