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Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels.

Hoe SZ, Lee CN, Mok SL, Kamaruddin MY, Lam SK - Clinics (Sao Paulo) (2011)

Bottom Line: The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro.Intravenous administrations of butanolic fraction elicited significant (p < 0.001) and dose-dependent decreases in the mean arterial pressure.However, a significant (p < 0.05) decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg).

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. hoesz@ummc.edu.my

ABSTRACT

Introduction: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied.

Objectives: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats.

Methods: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro.

Results: Intravenous administrations of butanolic fraction elicited significant (p < 0.001) and dose-dependent decreases in the mean arterial pressure. However, a significant (p < 0.05) decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg). In isolated preparations of rat aortic rings, phenylephrine (1 × 10⁻⁶ M)- or potassium chloride (8 × 10⁻² M)-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1 × 10⁻⁶ - 1 × 10⁻¹ g/ml) induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5 × 10⁻³ and 5.0 × 10⁻³ g/ml butanolic fraction, the contractions induced by phenylephrine (1 × 10⁻⁹-3 × 10⁻⁵ M) and potassium chloride (1 × 10⁻² - 8 × 10⁻² M) were significantly antagonized. The calcium-induced vasocontractions (1 × 10⁻⁴-1 × 10⁻²M) were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10⁻² M) medium, as well as in calcium- and potassium-free medium containing 1×10⁻⁶ M phenylephrine. However, the contractions induced by noradrenaline (1 × 10⁻⁶ M) and caffeine (4.5 × 10⁻² M) were not affected by butanolic fraction.

Conclusion: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

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Related in: MedlinePlus

Effect of butanolic fraction (BU) on CaCl2‐induced contraction in Ca2+‐free solution containing high K+ (60 mM). Concentration‐response curves for CaCl2 were determined in endothelium‐denuded aortic rings in the absence (without BU) and presence of BU (2.5×10‐3 or 5.0×10‐3 g/ml). Values are mean±S.E.M. (n = 6). ***p<0.001 compared with controls (without BU).
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f4-cln_66p143: Effect of butanolic fraction (BU) on CaCl2‐induced contraction in Ca2+‐free solution containing high K+ (60 mM). Concentration‐response curves for CaCl2 were determined in endothelium‐denuded aortic rings in the absence (without BU) and presence of BU (2.5×10‐3 or 5.0×10‐3 g/ml). Values are mean±S.E.M. (n = 6). ***p<0.001 compared with controls (without BU).

Mentions: As shown in Figure 4, pretreatment of BU attenuated the CaCl2‐induced contraction of denuded rat aorta exposed to Ca2+‐free medium containing high K+. Preincubation of the rings with BU at 2.5×10‐3 and 5.0×10‐3 g/ml significantly (p<0.001) reduced the Emax values for CaCl2 in a concentration‐dependent manner (Table 2). Similarly, the pEC50 values for CaCl2 were reduced (p<0.001) in the presence of BU.


Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels.

Hoe SZ, Lee CN, Mok SL, Kamaruddin MY, Lam SK - Clinics (Sao Paulo) (2011)

Effect of butanolic fraction (BU) on CaCl2‐induced contraction in Ca2+‐free solution containing high K+ (60 mM). Concentration‐response curves for CaCl2 were determined in endothelium‐denuded aortic rings in the absence (without BU) and presence of BU (2.5×10‐3 or 5.0×10‐3 g/ml). Values are mean±S.E.M. (n = 6). ***p<0.001 compared with controls (without BU).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3044591&req=5

f4-cln_66p143: Effect of butanolic fraction (BU) on CaCl2‐induced contraction in Ca2+‐free solution containing high K+ (60 mM). Concentration‐response curves for CaCl2 were determined in endothelium‐denuded aortic rings in the absence (without BU) and presence of BU (2.5×10‐3 or 5.0×10‐3 g/ml). Values are mean±S.E.M. (n = 6). ***p<0.001 compared with controls (without BU).
Mentions: As shown in Figure 4, pretreatment of BU attenuated the CaCl2‐induced contraction of denuded rat aorta exposed to Ca2+‐free medium containing high K+. Preincubation of the rings with BU at 2.5×10‐3 and 5.0×10‐3 g/ml significantly (p<0.001) reduced the Emax values for CaCl2 in a concentration‐dependent manner (Table 2). Similarly, the pEC50 values for CaCl2 were reduced (p<0.001) in the presence of BU.

Bottom Line: The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro.Intravenous administrations of butanolic fraction elicited significant (p < 0.001) and dose-dependent decreases in the mean arterial pressure.However, a significant (p < 0.05) decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg).

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia. hoesz@ummc.edu.my

ABSTRACT

Introduction: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied.

Objectives: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats.

Methods: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro.

Results: Intravenous administrations of butanolic fraction elicited significant (p < 0.001) and dose-dependent decreases in the mean arterial pressure. However, a significant (p < 0.05) decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg). In isolated preparations of rat aortic rings, phenylephrine (1 × 10⁻⁶ M)- or potassium chloride (8 × 10⁻² M)-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1 × 10⁻⁶ - 1 × 10⁻¹ g/ml) induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5 × 10⁻³ and 5.0 × 10⁻³ g/ml butanolic fraction, the contractions induced by phenylephrine (1 × 10⁻⁹-3 × 10⁻⁵ M) and potassium chloride (1 × 10⁻² - 8 × 10⁻² M) were significantly antagonized. The calcium-induced vasocontractions (1 × 10⁻⁴-1 × 10⁻²M) were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10⁻² M) medium, as well as in calcium- and potassium-free medium containing 1×10⁻⁶ M phenylephrine. However, the contractions induced by noradrenaline (1 × 10⁻⁶ M) and caffeine (4.5 × 10⁻² M) were not affected by butanolic fraction.

Conclusion: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

Show MeSH
Related in: MedlinePlus