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1 Kinesiology Department, University of Montreal, Montreal, Quebec, Canada H3C 3J7; 2 Sports Medicine Research Unit, Department of Rheumatology H, Bispebjerg Hospital and Copenhagen Muscle Research Center and 3 Department of Clinical Physiology, Bispebjerg Hospital, DK-2400 Copenhagen NV; and 4 Department of Medical Physiology, Panum Institute and Copenhagen Muscle Research Center, DK-2220 N Copenhagen, Denmark
The study
examined the implication of the renin-angiotensin system (RAS) in
regulation of splanchnic blood flow and glucose production in
exercising humans. Subjects cycled for 40 min at 50% maximal
O2 consumption (
O2 max)
followed by 30 min at 70% O2 max
either with [angiotensin-converting enzyme (ACE) blockade] or without
(control) administration of the ACE inhibitor enalapril (10 mg iv).
Splanchnic blood flow was estimated by indocyanine green, and
splanchnic substrate exchange was determined by the arteriohepatic
venous difference. Exercise led to an ~20-fold increase
(P < 0.001) in ANG II levels in the control group
(5.4 ± 1.0 to 102.0 ± 25.1 pg/ml), whereas this response
was blunted during ACE blockade (8.1 ± 1.2 to 13.2 ± 2.4 pg/ml) and in response to an orthostatic challenge performed
postexercise. Apart from lactate and cortisol, which were higher in the
ACE-blockade group vs. the control group, hormones,
metabolites, O2, and RER followed the
same pattern of changes in ACE-blockade and control groups during
exercise. Splanchnic blood flow (at rest: 1.67 ± 0.12, ACE
blockade; 1.59 ± 0.18 l/min, control) decreased during moderate exercise (0.78 ± 0.07, ACE blockade; 0.74 ± 0.14 l/min,
control), whereas splanchnic glucose production (at rest: 0.50 ± 0.06, ACE blockade; 0.68 ± 0.10 mmol/min, control) increased
during moderate exercise (1.97 ± 0.29, ACE blockade; 1.91 ± 0.41 mmol/min, control). Refuting a major role of the RAS for these
responses, no differences in the pattern of change of splanchnic blood
flow and splanchnic glucose production were observed during ACE
blockade compared with controls. This study demonstrates that the
normal increase in ANG II levels observed during prolonged exercise in
humans does not play a major role in the regulation of splanchnic blood flow and glucose production.
angiotensin-converting enzyme; exercise; arteriohepatic venous difference
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