Acupuncture reduces experimental renovascular hypertension through mechanisms involving nitric oxide synthases

Abstract

Objective: To test the hypothesis that acupuncture on stomach 36 point (ST-36) reduces hypertension by activating nitric oxide synthase signaling mechanisms.

Methods: The authors used the two-kidney, one-clip renal hypertension (2K1C) hamster model with electroacupuncture treatment.

Results: Thirty-minute daily electroacupuncture treatment for 5 days reduced mean arterial pressure from 160.0 +/- 7.6 to 128.0 +/- 4.3 mmHg (mean +/- SEM), compared to 115.0 +/- 7.2 mmHg in sham-operated hamsters. Electroacupuncture increased periarteriolar NO concentration from 309.0 +/- 21.7 nM to 417.9 +/- 20.9 nM in the 2K1C hamster cheek pouch microcirculation when measured with NO-sensitive microelectrodes. Hypertension reduced endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) proteins relative to the sham-operated control, as measured by Western blotting. Electroacupuncture prevented the reduction of eNOS and nNOS associated with hypertension and showed even higher eNOS and nNOS expressions than sham-operated control in stomach and cheek pouch tissues, which are on the stomach meridian. Analysis of liver tissue, a non-stomach-meridian organ, indicated that electroacupuncture did not have a significant benefit in terms of enhanced expressions of eNOS and nNOS in the treated 2K1C hypertensive group.

Conclusions: Activation of eNOS and nNOS is one of the mechanisms through which ST-36 electroacupuncture reduces blood pressure; this reduction works through the stomach meridian.

Figure 1

Electroacupuncture on ST-36 reduces mean arterial blood pressure in experimental renovascular hypertension. The bars represent the means ± SEM. The numbers in parentheses show the number of hamsters included in each group. EA, electroacupuncture. *p <.05 compared with nontreated renovascular hypertensive (2K1C) hamsters, #p < .05 compared with sham-operated hamsters.

Figure 2

Electroacupuncture on ST-36 increases periarteriolar NO concentration. The bar graph shows the maximal increments in response to treatment. The data represent the means ± SEM. The numbers in parentheses show the number of animals included in each group. EA, electroacupuncture. * p < .05 compared with nontreated 2K1C hamsters, #p < .05 compared with sham-operated hamsters.

Figure 3

Western blotting analysis of eNOS in hamster cheek pouch and stomach. The band intensities in the Western blots were divided by the band intensity of corresponding nontreated sham-operated hamster. The data represent the means±SEM. Each group represents 3 hamsters. EA, electroacupuncture. *p < .05 compared with nontreated 2K1C hamsters, #p < 0.05 compared with sham-operated hamsters. The lower panel shows representative Western blot bands for each group. 1: 2K1C, 2: 2K1C+EA, 3: sham-operated+EA, 4: sham-operated.

Figure 4

Western blotting analysis of nNOS in hamster cheek pouch and stomach. The band intensities in the Western blots were divided by the band intensity of corresponding nontreated sham-operated hamster. The data represent the means ± SEM. Each group represents 3 hamsters. EA, electroacupuncture. * p < .05 compared with nontreated 2K1C hamsters, #p < .05 compared with sham-operated hamsters. The lower panel shows representative Western blot bands for each group. 1: 2K1C, 2: 2K1C+EA, 3: sham-operated+EA, 4: sham-operated.

Figure 5

Western blotting analysis of eNOS and nNOS in liver. The band intensities from the Western blots were divided by the band intensity of corresponding nontreated sham-operated hamster. The data represent the means ± SEM. Each group represents 3 hamsters. EA, electroacupuncture. * p < .05 compared with nontreated 2K1C hamsters, #p < .05 compared with sham-operated hamsters. The lower panel shows representative Western blot bands for each group. 1: 2K1C, 2: 2K1C+EA, 3: sham-operated+EA, 4: sham-operated.