Wednesday Morning Poster Presentations: Posters displayed from 7:30 a.m.–12:30 p.m. One-hour author presentation times are staggered from 9:30–10:30 a.m., 10:30–11:30 a.m., and 11:30 a.m.–12:30 p.m.: A-26 Free Communication/Poster – Circulation: Blood Flow/Pressure Control WEDNESDAY, MAY 31, 2006 9:30 AM – 12:30 PM ROOM: Hall B
INTRODUCTION: Exercise is accompanied by a variety of hormonal changes, for example, circulating catecholamines concentrations progressively increase in an exercise intensity dependent manner. However the intensity or duration necessary to cause an increase in circulating non-adrenergic vasoconstrictor hormones such as angiotensin II (AngII) in humans remains undefined.
PURPOSE: We aimed to determine if both maximal exercise and long duration exercise at 55% VO2max resulted in an increase in circulating plasma concentrations of AngII.
METHODS: Heart rate was continuously recorded and plasma samples drawn from a femoral venous catheter were assayed for AngII, norepinephrine (NE), and epinephrine (EPI) immediately before and immediately following a maximal upright cycling test to exhaustion in 5 healthy subjects; (age = 27.2 ± 0.86 yrs, weight 79.8 ± 11.9 kgs, VO2max 3.15 l/min; 3 men, 2 women). The same measurements and plasma samples were then taken immediately prior to and at 20 min. intervals during an hour long upright cycling trial at 55% VO2max.
RESULTS: During the VO2maxtest heart rate (HR) increased significantly from 70.7 ±1.1 bpm at baseline to 173.3 ± 5.9 bpm at exhaustionp <0.05. HR also increased significantly during the 1 hour long cycling protocol from 71.1 ± 3.3 bpm to 130 ± 6 bpm, P <0.05, within the first 5 minutes of exercise and remained constant throughout the duration of the exercise. Plasma NE was significantly higher at the completion of the VO2max test (2.0 ± 0.3 vs. 8.0 ± 0.7 pmol/ml; P <0.05), as well as at min 20 the 55% VO2max cycling protocol 1.8 ± 0.3 vs. 4.8 ± 0.8 pmol/ml; P <0.05) with no significant changes in NE between mins. 20, 40, and 60. There was no significant change in plasma EPI during either protocol. Plasma ANGII was significantly increased at the end of the VO2maxtest when compared to baseline (24.7 ± 7 vs. 45.2 ± 8 pmol/ml; p <0.05). During the 50% VO2max protocol ANGII levels doubled at min 20 in the 3 subjects (p = 0.073) and remained unchanged for the duration of the protocol (p = 0.73).
CONCLUSION: Collectively these data demonstrate that circulating plasma concentrations of angiotensin II are significantly increased during maximal exercise to exhaustion and shows trends towards significance during long duration sub-maximal work. These results suggest that in addition to circulating catecholamines other non-adrenergic vasoactive hormones are released during exercise and may play an important role in the redistribution of cardiac output and the maintenance of arterial blood pressure that occurs during exercise. Supported in part by NHLBI grant # 045547.