Vasorelaxant and Hypotensive Effects of Galla chinensis in Rats

Abstract

Previous studies have revealed the medicinal and therapeutic effects of Galla chinensis. However, no studies have focused on the antihypertensive effects of G. chinensis. Therefore, we aimed to determine the vasorelaxant and hypotensive effects of G. chinensis 50% ethanolic extract (GCE). To evaluate the vascular relaxing effect of GCE, experiments were conducted using aortic segments dissected from Sprague Dawley rats. GCE showed a vasorelaxant effect via the nitric oxide/cyclic guanosine 3',5'-monophosphate pathway, inhibiting Ca²⁺ channels, and activating K⁺ channels. The hypotensive effects of GCE were evaluated in spontaneously hypertensive rats (SHRs). The SHRs were randomly divided into a control group and orally administered GCE group (100 or 300 mg/kg). The systolic and diastolic blood pressure decreased significantly by -19.47 ± 4.58% and -31.14 ± 7.66% in the GCE 100 mg/kg group, and -21.64 ± 2.40% and -31.91 ± 5.75% in the GCE 300 mg/kg group at 4 h after administration. Considering its vasorelaxant and hypotensive effects, our results indicate that GCE may be a valuable solution for the control of hypertension. However, further studies on the long-term administration and toxicity of GCE are required.

Keywords: Chinese gallnut; Galla chinensis; NO/cGMP pathway; blood pressure; cardiovascular diseases; endothelium; hypertension; hypotensive effect; spontaneously hypertensive rat; vasorelaxant.

Figure 1

High-performance liquid chromatography (HPLC) analysis of (A) Galla chinensis 50% ethanol extract (GCE) and (B) gallic acid. AU, Absorbance units.

Figure 2

Galla chinensis 50% ethanol extract (GCE)-induced concentration-dependent relaxation of the endothelium-intact [Endo(+)] or -removed [Endo(−)] aorta. To confirm the integrity of endothelium, aortas pre-constricted by phenylephrine (PE) were administered with acetylcholine (ACh). (A) Relaxation response to cumulative doses of GCE and (B) representative tracing. Data are shown as the means ± standard error of the mean (SEM) (n = 4–5). * p < 0.05, *** p < 0.001 vs. control.

Figure 3

Galla chinensis 50% ethanol extract (GCE)-induced concentration-dependent relaxation of aortic rings pre-incubated with N^G-nitro-L-arginine methyl ester (L-NAME), indomethacin, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or methylene blue (MB). Rings were constricted by phenylephrine (PE) before the GCE-induced relaxation. (A) Relaxation response to cumulative doses of GCE and (B) representative tracing. Data are shown as the means ± SEM (n = 5). *** p < 0.001 vs. control.

Figure 4

Inhibitory effect of Galla chinensis 50% ethanol extract (GCE) on vasoconstriction of endothelium-intact aortic rings induced by calcium chloride (CaCl₂). Rings were pre-treated with phenylephrine (PE) before the vasoconstriction by CaCl₂. (A) Contraction response to cumulative doses of GCE and (B) representative traces. Data are shown as the means ± SEM (n = 4–5). *** p < 0.001 vs. control.

Figure 5

Galla chinensis 50% ethanol extract (GCE)-induced concentration-dependent relaxation of the aortic rings pre-treated with barium chloride (BaCl₂), 4-aminopyridine (4-AP), or tetraethylammonium (TEA). Rings were constricted with phenylephrine (PE) before the GCE-induced relaxation. (A) Relaxation response to cumulative doses of GCE and (B) representative tracing. Data are shown as the means ± SEM (n = 4–6). *** p < 0.001 vs. control.

Figure 6

Effects of Galla chinensis 50% ethanol extract (GCE) on aortas constricted by angiotensin II. (A) Contraction response to cumulative doses of GCE and (B) representative traces. Data are shown as the means ± SEM (n = 5).

Figure 7

Hypotensive effect of Galla chinensis 50% ethanol extract (GCE). Blood pressure of spontaneously hypertensive rats was measured after GCE (100 and 300 mg/kg) administration. (A) Systolic blood pressure (SBP), (B) diastolic blood pressure (DBP), (C) percent changes in SBP, (D) percent changes in DBP. Data are shown as the means ± SEM (n = 6–7). * p < 0.05, ** p < 0.01 vs. control.