Exercise training modulation of inward rectifier potassium channels and control blood pressure in hypertensive rats
Chun Zi Jin Wenbo Liu Lan Cui
Yan Bian University Hospital, Yanji, Ji Lin Province
Objectives: This study aimed to explore the mechanisms underlying high blood pressure control by physical exercise through modulation of inward rectifier potassium channels.
Methods: Hypertension animal models with or without physical exercise were established. The blood pressure in the rat models was monitored by a tail-cuff method using a multi-channel multi-animal Coda Non-Invasive Blood Pressure System (Kent Scientific Corporation, USA). After 4 weeks of preparation of animal models, the deep femoral arteries were removed from the rats under inhalational anesthesia. The luminal diameter of vessels was measured using a vessel diameter image analysis system. The patch-clamp technique was used to measure the Kir current, and Western blotting assay was used to determine the expression level of the Kir 2.1 protein.
Results: 1. No statistically significant difference in the body weight, heart weight, ventricular+Septum weight, Right ventricular weight and (ventricular+Septum) weight/Right ventricular weight were found between the hypertension group and the hypertension-exercise group. 2. The systolic blood pressures and diastolic pressure two weeks after the angiotensin II injection (no other treatments) did not show significant differences between the hypertension group (systolic blood pressures: Week 0: 125±2.9 mmHg, Week 1: 148±2.8 mmHg, Week 2: 145±3.1 mmHg; diastolic pressure :Week 0: 93.5±2.9 mmHg, Week 1: 95±3 mmHg, Week 2: 110±2.9 mmHg) and the hypertension-exercise group(systolic blood pressures: Week 0: 125±2.9 mmHg, Week 1: 148.5±3 mmHg, Week 2: 144±2.9 mmHg; diastolic pressure: Week 0:93.5±2.9 mmHg, Week 1: 94.5±2.8 mmHg, Week 2: 110.5±3.1 mmHg) (both P>0.05). At Week 4 post-angiotensin II injection (i.e., two weeks of exercise treatment for the hypertension-exercise group), the systolic blood pressure showed statistically significant difference between the hypertension group (Week 4: 170±2.9 mmHg) and the hypertension-exercise group (Week 4: 148±2.8 mmHg), so did the diastolic blood pressure(Week 4: 125±2.8 mmHg v.s. 105±2.9 mmHg) (p<0.05).Compared to the hypertension group, the hypertension-exercise group exhibited remarkably effective control of blood pressure. 3. As indicated by the vessel diameter image analysis, the vasodilation response in the hypertension-exercise group was more significant, which could be suppressed by the blocker (50mM BaCl2) of the inward rectifier potassium channels. 4. The patch-clamp recording of the Kir current revealed that the Kir current in the hypertension-exercise group was larger than that of the hypertension group (p<0.05). In addition, the expression of the Kir 2.1 protein in the hypertension-exercise group was higher than that of the hypertension group, as indicated by Western blotting assay.
Conclusions: The present study investigated the effects of long-term exercise on cells, in particular its effect on blood-pressure control through increasing membrane Kir current. This study revealed that, long-term exercise can enhance the vasodilation capacity of vessels while such improvement is critical for improving the quality of life and reducing the risk of hypertension and related cardio-cerebral vascular complications in hypertension patients.