(Hypertension. 1999;34:768-772.)
© 1999 American Heart Association, Inc.
Scientific Contributions |
Exercise Reverses Peripheral Insulin Resistance in Trained L-NAME–Hypertensive Rats
From the Laboratory of Cardiovascular Physiology, Department of Physiology (K.D.A., G.G., J.F., P.D'A., V.L.A., L.R.P., T.G.F., M.C.I.), Basic and Health Science Institute, University of Rio Grande do Sul, Brazil; and the Hypertension Unit, Heart Institute (M.C.I.), São Paulo, Brazil.
Correspondence to Maria Cláudia Irigoyen, MD, PhD, Hypertension Unit, Heart Institute, São Paulo, Brazil, Av Enéas de Carvalho Aguiar, 44, São Paulo, São Paulo 05403-000. E-mail hipirigoyen{at}incor4.incor.usp.br
Abstract—Several studies
have demonstrated an increase in peripheral resistance to
insulin associated with hypertension. To assess the
hemodynamic and metabolic effects of
exercise training, normotensive and
N
-nitro-L-arginine methyl
ester (L-NAME)–hypertensive male Wistar rats were submitted to
low-intensity treadmill exercise training for 10 weeks and compared
with their sedentary controls. Blood pressure signals were obtained and
processed with a data acquisition system (CODAS, 1 kHz) to evaluate
mean arterial pressure, heart rate, autonomic control of
heart rate, and baroreflex sensitivity. Exercise training induced a
nonsignificant 6.5-mm Hg decrease in mean arterial
pressure in trained hypertensive rats (163±9 mm Hg) compared
with sedentary hypertensive rats (169.5±5.5 mm Hg). The
hypertensive groups showed impairment of baroreflex function in
response to changes in arterial pressure compared with
sedentary controls. Furthermore, exercise training improved the
tachycardic response to decreasing arterial pressure and
reduced intrinsic heart rate in trained control rats compared with all
other groups. Sedentary hypertensive rats presented a decrease
in body weight compared with normotensive animals. Basal evaluation of
the glucose/insulin ratio showed increased insulin resistance in
sedentary (28.4±3) and trained (23.5±2.7) hypertensive rats compared
with sedentary control rats (40.5±3). However, the glucose/insulin
ratio evaluated during the exercise session in trained rats showed an
improvement in insulin resistance (54.5±5 for control rats and 44±9
for hypertensive rats). In conclusion, L-NAME–induced hypertension is
accompanied by an increase in insulin resistance in rats. The
improvement in peripheral insulin sensitivity during
exercise and the body weight gain observed in trained hypertensive rats
may support the positive role of physical activity in the management
of hypertension.
Key Words: insulin resistance • hypertension • exercise • autonomic nervous system • baroreceptors
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