Long-term antihypertensive effects of far-infrared ray irradiated from wooden board in spontaneously hypertensive rats

Abstract

Background: Far-infrared ray (FIR) has been widely used in promoting health and has been shown to exert beneficial effects in vascular function. The non-thermal effect of FIR has been found to play a significant role in the protective effect on some vascular-related diseases, but its protective effects and use against hypertension have not been clearly presented.

Methods: In the present study, by using a wooden board coated with FIR-irradiated materials, we evaluated the long-term antihypertensive effect on spontaneously hypertensive rats (SHRs) in the environment in contact with the FIR-irradiated wooden board. SHRs were placed on the wooden board with or without FIR radiation for 4 weeks.

Results: The systolic blood pressure (BP) of SHRs undergoing different treatments was measured weekly using a tail-cuff method. FIR radiation significantly reduced the systolic BP of the SHRs along with a decreasing plasma level of angiotensin II and an increasing plasma level of bradykinin. In addition, long-term contact of FIR did not significantly affect the BP in normotensive Wistar Kyoto rats (WKYs).

Conclusions: Our results provided the evidence based on which FIR radiation could be considered an effective non-pharmacological choice for preventing hypertension.

Fig. 1

Changes in systolic BP of experimental rats during the 4-week period. a The SHRs were randomly divided into four groups (n = 10 per group). Group 1: SHRs on a wooden board without FIR radiation as the control group (control); group 2: SHRs on a wooden board with FIR radiation (FIR); group 3: SHRs on a normal wooden board with atenolol administration as the positive control group (atenolol); and group 4: SHRs on an FIR-radiated wooden board with atenolol administration (FIR + atenolol). b The WKY rats were randomly divided into two groups (n = 10 per group). Group 1: WKYs on a wooden board without FIR radiation as the control group (control); and group 2: WKY rats on a wooden board with FIR radiation (FIR). Data are mean ± SEM. *p < 0.05 vs. control SHRs, #p < 0.05 vs. SHRs with FIR irradiation

Fig. 2

Plasma ACE activity of experimental rats after the 4-week treatments. WKYs: WKYs on a wooden board without FIR radiation; CL: SHRs on a wooden board without FIR radiation; FIR: SHRs on a wooden board with FIR radiation; atenolol: SHRs on a normal wooden board with atenolol administration; FIR + atenolol: SHRs on an FIR-radiated wooden board with atenolol administration. Data are mean ± SEM from n = 10 animals per treatment group. *p < 0.05 vs. control SHRs, #p < 0.05 vs SHRs with FIR irradiation, †p < 0.05 vs. WKY group

Fig. 3

Plasma angiotensin II levels of experimental rats after the 4-week treatments. WKYs: WKYs on a wooden board without FIR radiation; CL: SHRs on a wooden board without FIR radiation; FIR: SHRs on a wooden board with FIR radiation; atenolol: SHRs on a normal wooden board with atenolol administration; FIR + atenolol: SHRs on an FIR-radiated wooden board with atenolol administration. Data are mean ± SEM from n = 10 animals per treatment group. *p < 0.05 vs. control SHRs, #p < 0.05 vs SHRs with FIR irradiation, †p < 0.05 vs. WKY group

Fig. 4

Plasma bradykinin levels of experimental rats after the 4-week treatments. WKYs: WKYs on a wooden board without FIR radiation; CL: SHRs on a wooden board without FIR radiation; FIR: SHRs on a wooden board with FIR radiation; atenolol: SHRs on a normal wooden board with atenolol administration; FIR + atenolol: SHRs on an FIR-radiated wooden board with atenolol administration. Data are mean ± SEM from n = 10 animals per treatment group. *p < 0.05 vs. control SHRs, #p < 0.05 vs. SHRs with FIR irradiation, †p < 0.05 vs. WKY group

Fig. 5

Plasma sICAM-1 (a), sVCAM-1 (b), and sE-selectin (c) levels of experimental rats after the 4-week treatments. WKYs: WKYs on a wooden board without FIR radiation; SHR-CL: SHRs on a wooden board without FIR radiation; SHR-FIR: SHRs on a wooden board with FIR radiation. Data are mean ± SEM from n = 10 animals per treatment group. *p < 0.05 vs. WKY group, #p < 0.05 vs. SHRs with FIR irradiation