Sl. Amaral et al., Exercise training causes skeletal muscle venular growth and alters hemodynamic responses in spontaneously hypertensive rats, J HYPERTENS, 19(5), 2001, pp. 931-940
Citations number
42
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Objective To investigate whether training changes skeletal muscle venular p
rofile and hemodynamic responses to exercise we studied spontaneously hyper
tensive rats (SHR) and Wistar-Kyoto (WKY) rats submitted to training progra
mme (T = 50-60% of VO(2)max).
Design Training (T) was performed on a treadmill over a period of 13 weeks.
Age-matched control groups were kept sedentary (S), T and S rats were chro
nically instrumented for hindlimb flow (HLF) and arterial pressure (AP) mea
surements at rest, during dynamic exercise and recovery in two different si
tuations: control and after extensive intravenous blockade (hexamethonium losartan + N-omega-nitro-L-arginine methyl ester + hydralazine), For morph
ometric analysis, skeletal muscle samples (gracilis) were obtained after tr
anscardiac perfusion with fixative.
Results T caused a significant reduction of resting mean arterial pressure
(MAP) (-11%) only in the SHR group without changing basal HLF. In the seden
tary SHR (SHRS), basal relative hindlimb resistance was increased by 45%, b
ut was significantly reduced after T (P < 0.05), During dynamic exercise, M
AP increased similarly (10-20 mm Hg) in all groups. HLF increases were simi
lar for the four groups up to 0.8 km/h; at higher workloads, HLF was higher
in trained SHR (SHRT) versus trained WKY (WKYT) (3.9- versus 2.9-fold incr
ease over basal HLF, respectively). After blockade (and pressure correction
with IV phenylephrine infusion), steady-state exercise was performed with
similar hindlimb vasodilation in all groups and was accompanied by MAP redu
ction (-17 <plus/minus> 8 mmHg) only in SHRT group. Skeletal muscle venular
profile (density, diameter and lumen cross-sectional area) was similar in
WKYT, WKYS and SHRS, but significantly increased in SHRT. In this group the
two-fold increase in venule density was correlated with both the reduction
in baseline MAP and the increase in HLF during dynamic exercise.
Conclusions The results suggest that increased venule density is a specific
adaptation of SHR skeletal muscle to training. Venular growth may contribu
te to both the pressure-lowering effect and the large HLF at high exercise
intensities observed in the trained SHR. J Hypertens 19:931-940 (C) 2001 Li
ppincott Williams & Wilkins.