Effects of high-intensity interval training on G protein-coupled receptor kinase-2 levels in the hearts and adrenal glands of spontaneously hypertensive rats / 中华物理医学与康复杂志

ABSTRACT

Objective@#To observe the effect of high-intensity interval training (HIIT) on G protein-coupled receptor kinase-2 (GRK2) levels in the hearts and adrenal glands of spontaneously hypertensive rats (SHRs) and explore how exercise might improve sympathetic over-excitation.@*Methods@#Twenty male SHRs were divided randomly into a sedentary control group and an HIIT group. Ten age-matched, male Wistar-Kyoto rats without hypertension served as the control group. The rats of the control and sedentary control groups were housed in cages at rest while those of the HIIT group underwent eight weeks of HIIT. Caudal artery pressure, cardiac structure and function, and heart rate variability (HRV) were determined using a non-invasive blood pressure tester, echocardiograms, and electrocardiograms. The plasma concentrations of epinephrine and norepinephrine, and the expression of GRK2 and β1-adrenoceptor (β1-AR) protein were measured in the rats′ hearts, and GRK2 and α2-adrenoceptor (α2-AR) protein were measured in their adrenal glands using high-pressure liquid chromatography and western blotting.@*Results@#Compared with the normotensive control group, animals in the sedentary control group showed elevated blood pressure, cardiac hypertrophy, reduced heart function, sympathetic over-excitation manifested by HRV, increased plasma epinephrine and norepinephrine concentrations, up-regulated GRK2 protein expression in the heart and adrenal gland, but down-regulated β1-AR in the heart and down-regulated α2-AR in the adrenal gland. Compared with the sedentary control group, the HIIT group did not show improved cardiac hypertrophy, but it did show reduced blood pressure, enhanced heart function, suppressed sympathetic over-excitation, as well as lowered plasma epinephrine and norepinephrine concentrations, on average. The expression of GRK2 in the heart and adrenal gland was significantly down-regulated, while that of β1-AR in the heart and of α2-AR in the adrenal gland were significantly up-regulated, on average.@*Conclusions@#HIIT can alleviate sympathetic over-excitation and enhance heart function despite spontaneous hypertension, at least in rats. The therapeutic mechanism may be related with the down-regulation of GRK2 expression in the heart and adrenal gland.