The effects of chronic treatment with Morus bombycis KOIDZUMI in spontaneously hypertensive rats

The present study was performed to evaluate the antihypertensive effects of Morus bombycis KOIDZUMI (MK) in spontaneously hypertensive rats (SHRs). In addition, the effects on vascular responses and cardiac functions were also investigated. In isolated rat aortic preparations, the 100% ethanol extract of MK exhibited a potent vascular relaxant effect with IC(50) value of 3.9 microg/ml, and this vasorelaxant effect was completely abolished by pretreatment of the aortic tissues with N(G)-nitro-L-arginine methyl ester or the denudation of endothelial layer. In isolated rat hearts, the MK extract significantly reduced cardiac functions such as left ventricular developed pressure and heart rate. In an antihypertensive study in SHRs, long-term administration with MK extracts (10, 30, 100 mg/kg) for 42 d dose-dependently decreased systolic blood pressure (approximately 20 mmHg). In SHRs, MK extract enhanced the aortic relaxation to acetylcholine and sodium nitroprusside after 42 d of treatment. In addition, lipid peroxidation and DNA damage in liver of SHRs were also attenuated by long-term treatment with MK extract. These results suggest that chronic treatment with MK extract exerts an antihypertensive effect in SHRs, and its direct vasorelaxant, negative inotropic actions, and anti-oxidant properties may contribute to reduce the elevated blood pressure.     

Involvement of nitric oxide in the mediation of the hypotensive action of the essential oil of Mentha x villosa in normotensive conscious rats

Recently, we showed that intravenous (i.v.) treatment with the essential oil of Mentha x villosa (EOMV) in pentobarbitone-anaesthetised rats decreased blood pressure; the effect occurred independently of the presence of an operational central autonomic drive to the cardiovascular system. This finding suggested that the hypotensive activity of EOMV may result from its vasodilatory effects directly upon vascular smooth muscle. The present study examines this possibility and whether EOMV-induced hypotension is mediated, at least in part, by an endothelial L-arginine/nitric oxide pathway. In conscious rats, i.v. injections of bolus doses (1 to 20 mg/kg) of EOMV elicited immediate and dose-dependent decreases in mean aortic pressure (MAP) and heart rate (HR). Pretreatment with i.v. hexamethonium (30 mg/kg) reduced the EOMV-induced bradycardia without affecting the hypotension. However, i.v. pretreatment with the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl (L-NAME, 20 mg/kg), reduced partially, but significantly, the maximal percent decreases in MAP elicited by EOMV without affecting the bradycardia. In rat isolated thoracic aorta preparations, EOMV (1 - 130 microg/ml) induced a concentration-dependent reduction of potassium (60 mM)-induced contraction. This smooth muscle-relaxant activity of EOMV was significantly reduced by the incubation of endothelium-intact rings with L-NAME (20 microM), as evidenced by the significant enhancement in the IC50 for EOMV-induced reduction of potassium-induced contraction (133.8 +/- 26.5 vs. 65.2 +/- 8.2 microg/ml in the absence of L-NAME). Furthermore, the vasorelaxant effects of EOMV in endothelium-denuded aortic rings were also significantly reduced (IC50 = 109 +/- 10 microg/ml), compared to those observed in segments with intact endothelium (IC50 = 61 +/- 13 microg/ml). These results show that i.v. treatment with EOMV dose-dependently decreases blood pressure in conscious rats, and that this action is due to an active vascular relaxation rather than withdrawal of sympathetic tone. Released nitric oxide from vascular endothelial cells appears partially involved in the aortic relaxation induced by EOMV and in turn in the mediation of EOMV-induced hypotension. They further support the concept that EOMV-induced hypotension and bradycardia occurred independently.     

Cytotoxic and antioxidant activity of Achillea alexandri-regis

The cytotoxicity and antioxidant properties of herb extracts of Achillea alexandri-regis were studied. Combined chloroform and ethylacetate extracts exhibited a pronounced cytotoxic effect against HeLa cancer cells (IC50 = 25.92 +/- 4.96 microg/ml), and lower cytotoxicity against K562 leukemia cells (IC50 = 48.59 +/- 18.31 microg/ml). The methanol extract was found to be a moderately cytotoxic in vitro agent against HeLa and K562 cells. No suppressive activity was detected on non-malignant peripheral blood mononuclear cells (PBMC). The antioxidant activity of the methanol extract was assessed by DPPH radical scavenging. The methanol extract of A. alexandri-regis showed concentration dependent DPPH radical scavenging activity with IC50 = 36.14 +/- 0.05 microg/ml.     

The effects of two types of pyrethroid on rat skeletal muscle

The mechanism and profile of antagonism of thromboxane receptors were studied in isolated perfused cat coronary arteries and in rat aortic rings. In cat coronary arteries, the thromboxane receptor antagonist (TxRA) BM-13,505 at concentrations from 3 to 300 ng/ml, significantly attenuated the vasoconstrictor effects of both a thromboxane A2 analog (CTA2) and an endoperoxide analog (U-46,619) and did not alter the constrictor responses to leukotriene D4, arginine vasopressin, or angiotensin II. In rat aortic rings precontracted by CTA2 or U-46,619, the effective threshold concentration of BM-13,505 for relaxation was 5 ng/ml. Lower concentrations of BM-13,505 exerted no relaxation, and higher concentrations exhibited faster relaxation to the precontracted baseline levels. This relaxation was not observed in aortic rings precontracted by norepinephrine or angiotensin II. The action of TxRA was not influenced by the absence of the endothelium or by pretreatment with a selective guanylate cyclase inhibitor, methylene blue. Also, thromboxane receptor antagonists do not appear to block thromboxane induced constriction by action as free radical scavengers. It can be concluded that replacing thromboxane A2 on the vascular receptor by a TxRA is the main factor responsible for the antagonism of thromboxane induced vasoconstriction in vascular smooth muscle preparations, not, the presence of the endothelium, activation of guanylate cyclase, or scavenging of superoxide free radicals.     

辛伐他汀对自发性高血压大鼠血管功能作用研究

目的观察口服20 mg.kg-1辛伐他汀对自发性高血压大鼠血压与血管功能作用。方法观察辛伐他汀口服7周高血压大鼠血压、血管反应性、NO2-/NO3-水平以及血管组织学变化。结果治疗7周后,各组大鼠体重、心率无显著性差别(P>0.05),辛伐他汀长期给药不能明显降低高血压大鼠收缩压(P>0.05)。大鼠血管对乙酰胆碱反应性明显改善(P<0.05),而对硝普钠反应性无明显变化(P>0.05);与对照组比较,辛伐他汀明显升高血清NO2-/NO3-水平,并能明显减少血管壁弹性膜层数以及中膜厚度(P<0.05)。结论辛伐他汀对自发性高血压大鼠有血管扩张作用以及改善血管重构等作用。但不能抑制自发性高血压大鼠血压的升高。     

Antioxidant properties of Aller-7, a novel polyherbal formulation for allergic rhinitis

Allergic rhinitis, a frequently occurring immunological disorder affecting men, women and children worldwide, is a state of hypersensitivity that occurs when the body overreacts to a substance such as pollen, mold, mites or dust. Allergic rhinitis exerts inflammatory response and irritation of the nasal mucosal membranes leading to sneezing; stuffy/runny nose; nasal congestion; and itchy, watery and swollen eyes. A novel, safe polyherbal formulation (Aller-7/NR-A2) has been developed for the treatment of allergic rhinitis using a unique combination of extracts from seven medicinal plants including Phyllanthus emblica, Terminalia chebula, Terminalia bellerica, Albizia lebbeck, Piper nigrum, Zingiber officinale and Piper longum. In this study, the antioxidant efficacy of Aller-7 was investigated by various assays including hydroxyl radical scavenging assay, superoxide anion scavenging assay, 1,1-diphenyl-2-picryl hydrazyl (DPPH) and 2,2-azinobis-ethyl-benzothiozoline-sulphonic acid diammonium salt (ABTS) radical scavenging assays. The protective effect of Aller-7 on free radical-induced lysis of red blood cells and inhibition of nitric oxide release by Aller-7 in lipopolysaccharide-stimulated murine macrophages were determined. Aller-7 exhibited concentration-dependent scavenging activities toward biochemically generated hydroxyl radicals (IC50 741.73 microg/ml); superoxide anion (IC50 24.65 microg/ml by phenazine methosulfate-nicotinamide adenine dinucleotide [PMS-NADH] assay and IC50 4.27 microg/ml by riboflavin/nitroblue tetrazolium [NBT] light assay), nitric oxide (IC50 16.34 microg/ml); 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical (IC50 5.62 microg/ml); and 2,2-azinobis-ethyl-benzothiozoline-sulphonic acid diammonium salt (ABTS) radical (IC50 7.35 microg/ml). Aller-7 inhibited free radical-induced hemolysis in the concentration range of 20-80 microg/ml. Aller-7 also significantly inhibited nitric oxide release from lipopolysaccharide-stimulated murine macrophages. These results demonstrate that Aller-7 is a potent scavenger of free radicals and that it may serve.     

Antioxidant activity of four endemic Stachys taxa

Methanol extracts of aerial flowering parts of four endemic Stachys taxa: S. anisochila VIS. et PANCIC, S. beckeana DORFLER & HAYEK, S. plumosa GRISEB. and S. alpina L. ssp. dinarica MURB. were investigated on their antioxidant activity. The extracts were studied for total antioxidant activity (TAA), along with 1,1-diphenyl 2-picryl hydrazyl (DPPH) and OH radical scavenging activity, and lipid peroxidation (LP). High correlations between total phenolics content, TAA and scavenging DPPH radical indicate that polyphenols are the main antioxidants. All Stachys extracts, with the exception of S. plumosa, exhibited high anti-DPPH activity (IC50<50 microg/ml). In concentration range from 6.25 to 50 microg/ml, all extracts scavenged OH radical above 40%, with maximal inhibitions for S. anisochila, S. alpina ssp. dinarica and S. beckeana extracts of 50.22%, 50.94% and 64.97%, respectively. Only S. plumosa extract achieved maximal activity of 60.67% at 100 microg/ml. As for LP, IC50 values for S. beckeana and S. alpina ssp. dinarica extracts were 25.07 and 49.00 microg/ml, respectively, while S. anisochila and S. plumosa extracts did not reach 50% of LP inhibition.     

Antioxidant and free radical-scavenging activity of Choto-san and its related constituents

The antioxidant properties of Choto-san and its related constituents such as Chotoko and Choto-san without Chotoko, and phenolic compounds contained in Chotoko such as epicatechin, caffeic, acid and quercetin were evaluated. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, the scavenging activity of Chotoko (IC(50) 14.3 microg/ml) was found to be higher than that of Choto-san (IC(50) 206.2 microg/ml) and Choto-san without Chotoko (IC(50) 244.3 microg/ml). Epicatechin (IC(50) 10.4 microM), caffeic acid (IC(50) 13.8 microM), and quercetin (IC(50) 7.1 microM) also revealed scavenging activity against DPPH radicals. Choto-san (IC(50) 67.7 microg/ml) exhibited stronger inhibitory activity against superoxide anion formation than Choto-san without Chotoko (IC(50) 92.4 microg/ml) but weaker activity than Chotoko (IC(50) 18.3 microg/ml). The generation of superoxide anion was also inhibited by epicatechin (IC(50) 175.2 microM), caffeic acid (IC(50) 141.7 microM), and quercetin (IC(50) 18.7 microM). In a hydroxyl radical-scavenging experiment, Choto-san (IC(50) 2.4 mg/ml), Chotoko (IC(50) 2.2 mg/ml), Choto-san without Chotoko (IC(50) 2.8 mg/ml), epicatechin (IC(50) 3.9 mM), caffeic acid (IC(50) 3.6 mM), and quercetin (IC(50) 1.9 mM) exhibited activity. In NG108-15 cells, when added simultaneously with H(2)O(2) (500 microM), Choto-san (250 microg/ml), Chotoko (250 microg/ml), Choto-san without Chotoko (500 microg/ml), epicatechin (200 microM), caffeic acid (200 microM), and quercetin (200 microM) effectively protected cells from oxidative damage. In conclusion, the present results provide evidence that Choto-san acts as an antioxidant and cytoprotective agent against oxidative damage, which is due at least partly to the phenolic compounds contained in Chotoko.     

Involvement of nitric oxide, but not prostaglandins, in the vascular sympathoinhibitory effects of losartan in the pithed spontaneously hypertensive rat.

1. The aim of this study was to investigate whether nitric oxide (NO) and/or vasodilator prostaglandins (PGs) are involved in the sympathoinhibitory effects exerted by losartan versus the vascular responses elicited by spinal cord electrical stimulation (SCS) in pithed spontaneously hypertensive rats (SHRs). 2. SHRs were given orally and for 8 days either losartan (10 mg kg-1 daily) or distilled water (controls). After pithing, blood pressure, heart rate, cardiac output, renal and muscular blood flows (pulsed Doppler technique) and the corresponding vascular resistance values were measured or calculated at baseline. Then, animals from both groups were given i.v. either saline, or NG-nitro-L-arginine methyl ester (L-NAME, 1 mg kg-1), or diclofenac (4 mg kg-1). Thereafter, haemodynamic parameters were determined in the six subgroups of animals in response (a) to SCS at increasing frequencies, and (b) to a noradrenaline bolus injection. 3. Losartan significantly decreased mean arterial pressure as well as renal and total peripheral resistances. In addition, losartan exhibited strong vascular sympathoinhibitory effects, significantly decreasing the systemic pressor and regional vasoconstrictor responses to SCS, but did not affect those to exogenous noradrenaline. In contrast, SCS-induced tachycardia was not modified by losartan. 4. L-NAME significantly increased total peripheral and regional vascular resistances but did not affect blood pressure and heart rate basal values. L-NAME potentiated the haemodynamic responses to SCS in control and, to a larger extent, in losartan-treated SHRs so that, with the exception of the renal vascular bed, the sympathoinhibitory effects of losartan were attenuated in all vascular beds studied. L-Arginine (300 mg kg-1) caused reversal of L-NAME effects in both control and losartan-treated SHRs. 5. Diclofenac did not affect the basal values of haemodynamic parameters in control and losartan-treated SHRs. Diclofenac potentiated the pressor and vasoconstrictor responses to SCS and to a similar extent, in both control and losartan-treated SHRs, so that the sympathoinhibitory effects of losartan were fully maintained. 6. These results demonstrate that in pithed SHRs: (a) NO but not PGs contribute to the basal vasomotor tone, (b) both NO and PGs attenuate the pressor and vasoconstrictor responses to SCS, (c) NO plays a major role in the vascular sympathoinhibitory effects of losartan, except at the renal level, and (d) endogenous PGs are not involved in these sympathoinhibitory effects.     

Evaluation of pharmacokinetics and pharmacodynamics of captopril from transdermal hydrophilic gels in normotensive rabbits and spontaneously hypertensive rats

The purpose of this investigation was to assess the pharmacokinetics (plasma concentration) and pharmacodynamics (heart rate, blood pressure (BP), and plasma renin activity (PRA)) of captopril experimental gel in normotensive rabbits and spontaneously hypertensive rats (SHRs) by reference to a short duration intravenous administration of the drug. In normotensive rabbits, the blood concentration versus time course of captopril after transdermal administration could be described well by a two-compartment model, and the maximum plasma concentration (5. 68+/-2.05 microg ml(-1)) was achieved in about 7 h. The increase in plasma captopril concentration led to increases in PRA and reductions in BP. A simple E(max) model adequately described the relationship between the percentage change of mean blood pressure (MBP) and the blood concentration of the captopril. The maximum reduction in MBP (E(max)) was 36.23% and the concentration at half maximum effect (EC(50)) was 0.24 microg ml(-1). The captopril was continuously released from the gel formulation and protected the SHRs in lower BP throughout the period of transdermal therapy. These results indicated that the development of captopril transdermal drug delivery system was possible. Further research was warranted on a modified formulation of captopril, which was optimized for transdermal delivery of the drug.     

Characterization of the radical scavenging and antioxidant activities of danshensu and salvianolic acid B.

Danshensu (3-(3,4-dihydroxyphenyl) lactic acid) and salvianolic acid B, two natural phenolic acids of caffeic acid derivatives isolated from Salvia miltiorrhiza root of the most widely used traditional Chinese medicine for the treatment of various cardiovascular diseases, have been reported to have potential protective effects from oxidative injury. To better understand their biological functions, the in vitro radical scavenging and antioxidant activities of danshensu and salvianolic acid B were evaluated along with vitamin C. Both danshensu and salvianolic acid B exhibited higher scavenging activities against free hydroxyl radicals (HO()), superoxide anion radicals (O(2)(-)), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals than vitamin C. In contrary, danshensu and salvianolic acid B showed weaker iron chelating and hydrogen peroxide (H(2)O(2)) scavenging activities than vitamin C. As expressed as vitamin C equivalent capacity (VCEAC), the relative VCEAC values (mg/100ml) were in the order of salvianolic acid B (18.59) > danshensu (12.89) > vitamin C (10.00) by ABTS radical assay. The protective efficiencies against hydrogen peroxide induced human vein vascular endothelial cell damage were correlated with their antioxidant activities. Analysis of structure-activity relationship of these two compounds showed that the condensation and conjugation of danshensu and caffeic acid appears important for antioxidant activity. These results indicated that danshensu and salvianolic acid B are efficient radical scavengers and antioxidants, and salvianolic acid B is superior to danshensu. Their radical scavenging and antioxidant properties might have potential applications in food and healthcare industry.     

Chemical composition and antioxidant activity of volatiles from Patrinia Villosa Juss obtained by optimized supercritical fluid extraction

Supercritical CO(2) fluid extraction (SFE-CO(2)) was used to extract volatiles from Patrinia Villosa Juss. An orthogonal test L(9) (3)(4) including pressure, temperature, dynamic extraction time and modifier was performed to get the optimal conditions. Extract 1 was obtained by the optimal extraction condition 1: pressure=35 MPa, T=45 degrees C, dynamic extraction time=2.0 h and V(modifier (MeOH))=0% as guided by the index 1: the free radical scavenging activities in vitro against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethyl-benzthiazoline-6-sulfonic acid) diammonium salt (ABTS). Extract 2 obtained by the optimal extraction condition 2: pressure=25 MPa, T=55 degrees C, dynamic time=2.5h and V(modifier (MeOH))=20% was guided by the index 2: the yield of the volatiles. The results showed that extract 1 possessed stronger antioxidant activity (EC(50)=32.01 microg/ml to DPPH and 50.90 microg/ml to ABTS(+)) than the extract 2 (EC(50)=95.62 microg/ml to DPPH and 99.78 microg/ml to ABTS(+)). Subsequently, the chemical compositions of the two extracts were identified by gas chromatography-mass spectrometry. Forty-six compounds were identified from extract 1, and the total volatile consisted of hydrocarbon (49.65%), aldehyde (16.66%), fatty acid (22.38%), terpene (9.04%) and little alcoholic. From extract 2, 32 compounds were identified, in which hydrocarbon, aldehyde, fatty acid and terpene possessed 58.21%, 5.97%, 13.19% and 21.79%, respectively. This is the first report of using SFE to extract the volatiles from P. Villosa Juss (a wild vegetable and medicine plant) and first time to systematically evaluate the volatiles' antioxidant activity and chemical composition.     

Ketanserin: systemic and regional hemodynamics in spontaneously hypertensive rats. Role of alpha 1-adrenoceptor blockade

The systemic and regional hemodynamic effects of ketanserin were investigated in spontaneously hypertensive rats (SHRs) using either the pulsed Doppler or the microsphere technique. In addition, the contribution of ketanserin alpha 1-adrenoceptor blocking properties to these hemodynamic effects was assessed. Ketanserin, directly after infusion or secondarily after bolus injection, induced dose-dependent decreases in blood pressure and regional vascular resistances. Peripheral vasodilatation was not homogeneous, affecting in a decreasing rank order: muscle = spleen greater than brain = kidney = total peripheral resistance = liver greater than mesentery = skin. Cardiac output and hindlimb blood flow increased, renal blood flow was maintained whereas mesenteric blood flow was decreased. Prazosin pretreatment, followed by PGF 2 alpha infusion in order to restore initial vascular tone, reduced the ketanserin-induced decrease in blood pressure (by about 70%) and abolished the drug-induced reductions in regional vascular resistances, indicating that these effects in SHRs were mostly due to the alpha 1-adrenoceptor blocking properties of the drug.     

In vitro Antioxidant and Antibacterial Activities of Methanol Extract of Kyllinga nemoralis

The present study was designed to evaluate the antioxidant and antibacterial activity of methanol extract of Kyllinga nemoralis. Six different in vitro antioxidant assays including 2,2-diphenyl-1-picrylhydrazyl, hydroxyl radical, superoxide anion radical, hydrogen peroxide radical, ferric reducing antioxidant power assay and reducing power were carried out to ensure the scavenging effect of the plant on free radicals. In addition, total antioxidant capacity assay, total phenolic contents, tannins, flavonoids and flavonol contents of the plant were also analysed by the standard protocols. Kyllinga nemoralis exhibited high antioxidant activity on 2,2-diphenyl-1-picrylhydrazyl assay (IC₅₀= 90 μg/ml), superoxide radical scavenging assay (IC₅₀= 180 μg/ml) and hydrogen peroxide radical scavenging assay (IC₅₀= 200 μg/ml), compared with standards. These observations provide comprehensible supporting evidence for the antioxidant potential of the plant extract. Reducing power (IC₅₀= 213.16 μg/ml) and hydroxyl radical scavenging activity (IC₅₀= 223 μg/ml) of the plant extract was remarkable. The methanol extract of K. nemoralis exhibited significant antimicrobial activity against Gram-positive human pathogenic bacteria. Standard in vitro antioxidant assays assessed the electron donating ability of the plant extract in scavenging free radicals. The inhibitory effect of the plant extract against bacterial pathogens may be due to the presence of phytochemicals. Thus, the results suggest that Kyllinga nemoralis is a potential source of antioxidants and could serve as the base for drug development.     

Protection of the hemopoietic system by Podophyllum hexandrum against gamma radiation-induced damage

A semi-purified extract of low-altitude Podophyllum hexandrum (REC-2001) containing a relatively low content of podophyllotoxin (3.25 %) exhibited potent antioxidant ability in lipid media (at 1000 microg/mLagainst 0.25 kGy) and significant (p < 0.05) hydroxyl ion scavenging potential (78.83 % at 500 microg/mL). In vitro investigations revealed the ability of REC-2001 to significantly (p < 0.05) reduce radiation-induced hemolysis (2 microg/mL; 46.184 %) and nitric oxide scavenging levels (IC (50): 792 +/- 1.25 microg/mL). Protection of the hemopoietic system of Strain 'A' mice administered 20 mg/kg BW REC-2001 30 min prior to lethal irradiation (10 Gy) was recorded and was mediated by free radical scavenging and lowering of lipid oxidation. Further studies investigating the effects of REC-2001 on stem cell modulation are warranted.     

Isolation of luteolin 7-O-rutinoside and esculetin with potential antioxidant activity from the aerial parts ofArtemisia montana

The antioxidant activity of Artemisia montana was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibitory activity against free radical generation of hepatocytes (AC2F). The methanol extract of A. montana showed strong radical scavenging activity at a concentration of 10.1 microg/ml, and thus fractionated by solvent extraction. Esculetin and luteolin 7-O-rutinoside (scolymoside) were isolated as the active principles from the EtOAc and Interphase fractions, respectively. The antioxidant activity of these compounds were comparable to that of L-ascorbic acid.     

Effects of Ginkgo biloba extract on blood pressure and vascular endothelial response by acetylcholine in spontaneously hypertensive rats

We previously demonstrated that Ginkgo biloba extract (Ginkgo) produced vasodilation via the nitric oxide pathway in aortic segments isolated from Wistar rats. In this study, we have analysed the effects of daily long-term oral Ginkgo treatment on blood pressure, vascular tone, and calcium mobilization to evaluate the clinical availability. Spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were fed either a control diet or a diet containing 0.05%-0.5% Ginkgo for 30 days. Administration of Ginkgo did not change systolic blood pressure in WKY, but significantly decreased systolic blood pressure in SHR. In thoracic aortic preparations isolated from SHR, diminished relaxation in response to acetylcholine was improved by a Ginkgo-containing diet. This diet significantly decreased the EC50 value and significantly increased maximum relaxation in response to acetylcholine in SHR. In aortic segments isolated from WKY, acetylcholine-induced relaxation was not affected by a Ginkgo-containing diet. Sodium nitroprusside-induced relaxation was unchanged by a Ginkgo-containing diet in SHR and WKY. We also examined the effects of a Ginkgo-containing diet on the intracellular calcium level of aortic endothelium using a fluorescent confocal microscopic imaging system. Calcium Green 1/AM preloading indicated that acetylcholine significantly increased the endothelial intracellular calcium level. The Ginkgo-containing diet significantly enhanced this increase in the aortic endothelium of SHR, but did not change that of WKY. The results suggested that Ginkgo enhanced endothelium-dependent vasodilation and elevation of the endothelial intracellular Ca(2+) level in SHR, resulting in hypotension. This accelerative effect of Ginkgo on Ca(2+) mobilization seemed to be associated with restoration of impaired dilatory function induced by acetylcholine in endothelial cells.     

Effects of vitamin C and of a cell permeable superoxide dismutase mimetic on acute lipoprotein induced endothelial dysfunction in rabbit aortic rings

Low density lipoprotein (LDL) inhibits endothelium-dependent relaxation. The mechanism is uncertain, but increased production of superoxide anion O2- with inactivation of endothelium-derived NO and formation of toxic free radical species have been implicated. We investigated effects of the cell permeable superoxide dismutase mimetic manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin (MnTMPyP), the free radical scavenger vitamin C and arginine (which may reduce O2- formation) on acute LDL-induced endothelial dysfunction in rabbit aortic rings, using LDL prepared by ultracentrifugation of plasma from healthy men and aortic rings from New Zealand white rabbits. LDL (150 microg protein ml(-1) for 20 min) markedly inhibited relaxation of aortic rings (in Krebs' solution at 37 degrees C and pre-constricted to 80% maximum tension with noradrenaline) to acetylcholine 82+/-10% (mean percentage difference between sum of relaxations after each concentration of acetylcholine in the presence and absence of LDL, +/-s.e.mean, n=26, P<0.001) but not to the endothelium-independent agonist nitroprusside. MnTMPyP (10 microM) reduced inhibitory effects of LDL from 124+/-27 to 56+/-17% (n=6, P<0.05). Vitamin C (1 mM) reduced inhibitory effects of LDL from 59+/-8 to 22+/-5% (n=6, P<0.05). Inhibitory effects of LDL were similar in the absence or presence of arginine (84+/-12 vs 79+/-16%, n=14, P=0.55). Effects of L-arginine (10 mM) did not differ significantly from those of D-arginine (10 mM). Acute (20 min) exposure of aortic rings to LDL impairs endothelium-dependent relaxation which can be partially restored by MnTMPyP and vitamin C. This is consistent with LDL causing increased O2- generation.     

In vitroantioxidant properties of dantrolene sodium

Dantrolene sodium is a skeletal muscle relaxant, which inhibits intracellular Ca2+ release from the sarcoplasmic reticulum. The aim of this study is to examine possible in vitro antioxidant effects of dantrolene sodium. For this reason, the in vitro antioxidant effects of dantrolene sodium were studied using thiocyanate methods. Additionally, the reducing power and free radical scavenging activity were determined. Dantrolene sodium showed strong antioxidant activity in the linoleic acid emulsion system. The antioxidant activity increased with an increasing amount of dantrolene sodium (50, 100, 250 microg). The 50, 100 and 250 microg samples of dantrolene sodium showed 55%, 70% and 82% inhibition on peroxidation of linoleic acid, respectively. On the other hand, the 250 microg sample of alpha-tocopherol showed 62% inhibition of peroxidation of linoleic acid. Like antioxidant activity, the reducing power of dantrolene sodium increased in a dose-dependent manner. The reducing power of dantrolene was statistically significant vs control, but lower than butylated hydroxytoluene (BHT) and quercetin. Although dantrolene sodium had free radical scavenging activity this was not statistically significant. In contrast to dantrolene sodium, quercetin and butylated hydroxyanisole (BHA) had highly potent free radical scavenging activities and those were statistically significant. According to the these results, it may be said that antioxidant effect of dantrolene sodium is more related to its antioxidant activity in linoleic acid emulsion and reducing power, than to its free radical scavenging activity. These properties may be major reasons for the inhibition of lipid peroxidation.     

Cardiovascular effects of an n-butanol extract from fresh fruits of Randia siamensis

Randia siamensis is used in Thai folklore medicine for inducing abortion and controlling blood pressure. The present study investigated the cardiovascular effects of an R. siamensis fruit extract, and mechanisms involved in anesthetized normal and reserpinized rats. R. siamensis (0.4-12 mg/kg) i.v. increased the mean arterial pressure (MAP) and heart rate. Both effects were significantly inhibited by phentolamine (2 mg/kg, i.v.) or propranolol (0.6 mg/kg, i.v.). The combination of phentolamine and propranolol, or reserpine pretreatment, inhibited the positive chronotropic effect with a slight decrease in the MAP. In vitro, R. siamensis (0.001-0.3 mg/ml) increased the rate of beating of the right atrium and the strength of the electrical field-stimulated contraction of the left atrium, both effects were inhibited by propranolol, or with reserpine pretreated rats. R. siamensis (0.01-3 mg/ml) produced a contraction of isolated thoracic aorta, which was potentiated by N(G)-nitro-L-arginine (LNA), or by removal of the vascular endothelium, but inhibited by phentolamine, or reserpine. R. siamensis (0.3-3 mg/ml) caused a relaxation of phenylephrine-preconstricted aortic rings, which was potentiated with reserpine pretreatment, and abolished after removal of the vascular endothelium, or in the presence of LNA. These results suggest that R. siamensis extract exerts both hypertensive and positive chronotropic effects via the alpha- and beta-adrenergic receptors of blood vessels and the heart, due to release of endogenous catecholamines, likely from nerve ending and adrenal medulla. The hypotensive activity results from the release of nitric oxide causing dilatation of the blood vessels. The present data support the folklore therapeutic uses of this plant.