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Exploring the therapeutic potential of Anastatica hierochuntica essential oil in DSS-induced colitis. Inflammopharmacology 2024:10.1007/s10787-024-01449-4. [PMID: 38520575 DOI: 10.1007/s10787-024-01449-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Accepted: 02/23/2024] [Indexed: 03/25/2024]
Abstract
The aim of this investigation was to explore the protective impacts and mechanisms of Anastatica hierochuntica essential oil (EOAH) against dextran sulfate sodium (DSS)-induced experimental colitis in mice. EOAH demonstrated a reduction in DSS-induced body weight decline, disease activity index (DAI), colon length reduction, colonic tissue damage, and myeloperoxidase (MPO) activity. The essential oil significantly mitigated the production of pro-inflammatory agents including TNF-α, IL-1β, and IL-12. Further analysis revealed that EOAH's anti-inflammatory effects involved the regulation of NF-κB and PPARγ pathways, as well as the inhibition of NLRP3 activation in colitis mice. Notably, EOAH treatment elevated the levels of beneficial commensal bacteria such as Lactobacillus and Bifidobacteria, while reducing Escherichia coli levels in the mice's feces. In addition, EOAH restored the expression of occludin and ZO-1 proteins in colonic tissues affected by ulcerative colitis (UC). These findings indicate that supplementing with EOAH might offer a novel therapeutic approach for UC prevention.
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Isorhamnetin as a potential therapeutic agent for diabetes mellitus through PGK1/AKT activation. Arch Physiol Biochem 2024:1-11. [PMID: 38445617 DOI: 10.1080/13813455.2024.2323947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 02/20/2024] [Indexed: 03/07/2024]
Abstract
CONTEXT Type 2 Diabetes Mellitus (T2D) is a significant health concern worldwide, necessitating novel therapeutic approaches beyond conventional treatments. OBJECTIVE To assess isorhamnetin's potential in improving insulin sensitivity and mitigating T2D characteristics through oxidative and glycative stress modulation. MATERIALS AND METHODS T2D was induced in mice with a high-fat diet and streptozotocin injections. Isorhamnetin was administered at 10 mg/kg for 12 weeks. HepG2 cells were used to examine in vitro effects on stress markers and insulin sensitivity. Molecular effects on the PGK1 and AKT signalling pathway were also analyzed. RESULTS The administration of isorhamnetin significantly impacted both in vivo and in vitro models. In HepG2 cells, oxidative and glycative stresses were markedly reduced, indicating a direct effect of isorhamnetin on cellular stress pathways, which are implicated in the deterioration of insulin sensitivity. Specifically, treated cells showed a notable decrease in markers of oxidative stress, such as malondialdehyde, and advanced glycation end products, highlighting isorhamnetin's antioxidant and antiglycative properties. In vivo, isorhamnetin-treated mice exhibited substantially lower fasting glucose levels compared to untreated T2D mice, suggesting a strong hypoglycemic effect. Moreover, these mice showed improved insulin responsiveness, evidenced by enhanced glucose tolerance and insulin tolerance tests. The molecular investigation revealed that isorhamnetin activated PGK1, leading to the activation of the AKT signalling pathway, crucial for promoting glucose uptake and reducing insulin resistance. This molecular action underscores the potential mechanism through which isorhamnetin exerts its beneficial effects in T2D management. DISCUSSION The study underscores isorhamnetin's multifaceted role in T2D management, emphasizing its impact on oxidative and glycative stress reduction and molecular pathways critical for insulin sensitivity. CONCLUSION Isorhamnetin presents a promising avenue for T2D treatment, offering a novel approach to enhancing insulin sensitivity and managing glucose levels through the modulation of key molecular pathways. Further research is needed to translate these findings into clinical practice.
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Lysionotin exerts antinociceptive effects in various models of nociception induction. Heliyon 2023; 9:e15619. [PMID: 37151635 PMCID: PMC10161701 DOI: 10.1016/j.heliyon.2023.e15619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 04/13/2023] [Accepted: 04/18/2023] [Indexed: 05/09/2023] Open
Abstract
Background Lysionotin, a natural flavonoid extracted from Lysionotus pauciflorus Maxim (Gesneriaceae), has several pharmacological effects including anti-bacterial, anti-hypertensive and anti-inflammatory effects. However, its analgesic effect has not been investigated. This study aimed to assess the antinociceptive activity of lysionotin using chemically and thermally induced nociception in a mouse model. Methods The antinociceptive effects of various lysionotin doses (50, 100, 150, and 200 μg/kg) were assessed in mice using the acetic acid-induced writhing test, hot plate test, and formalin-induced paw licking assay. The effects were compared to those of mice treated with acetylsalicylic acid or morphine in the presence or absence of naloxone (an opioid receptor antagonist). Capsaicin- and glutamate-induced paw licking tests were also used to evaluate the involvement of the vanilloid and glutamatergic systems, respectively. Results Lysionotin produced significant dose-dependent inhibition of nociceptive behavior in the acetic acid-induced writhing test, showing 60% inhibition at a dose of 200 μg/kg. Lysionotin also caused a significant increase in the latency period in response to the hot plate test (76.4% at 200 μg/kg), and significantly inhibited both the neurogenic and inflammatory phases in the formalin-induced paw licking test. Naloxone significantly reverses the effect of lysionotin in both hot plate test and formalin-induced paw licking test. Moreover, lysionotin significantly inhibited the neurogenic nociception induced by intraplantar injections of glutamate and capsaicin (57% and 67.2%, respectively at a dose of 200 μg/kg). Thus, lysionotin exhibited peripheral and central antinociception through the modulation of vanilloid receptors, opioid receptors, and the glutamatergic system. Conclusion Lysionotin possesses antinociceptive activity on adult mice that is mediated through both central and peripheral pathways.
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Ethanol Extracts of Eriobotrya japonica (Loquat) Seeds, Leaves, and Fruits Have Anti-obesity and Hypolipidemic Effects in Rats. Pharmacogn Mag 2022. [DOI: 10.1177/09731296221137432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
Abstract
Background: Obesity is a serious public health problem contributing to development of several diseases, including hyperlipidemia, hyperglycemia, and hypertension. The plant Eriobotrya japonica (loquat) has been used in traditional Chinese medicine to treat many ailments and traditional healers used it to reduce weight. Objective: To examine the potential anti-obesity and hypolipidemic effects of ethanol extract of loquat in rats. Materials and Methods: Loquat leaves, fruits, or seeds were extracted with ethanol. About 96 Wistar male rats were fed either a normal rat diet (normal control group; group 1) or a high-fat diet (HFD) for 12 weeks (obese; groups 2−12). Obese rats were divided into11 groups as follows: (obese control: group 2) (obese positive control which received the hypolipidemic reference drug atorvastatin: group 3). Groups (4−6), (7−9), and (10−12) were given seed, leaf, or fruit extract, respectively, at 40,100, and 400 mg/kg. Body weight, serum glucose, lipid profile, creatinine, liver enzymes, albumin, and total protein were measured weekly. Results: HFD consumption significantly increased body weight and serum total cholesterol (TC), triglycerides (TGs), low-density lipoprotein (LDL), very-low density lipoprotein (VLDL), and glucose and decreased HDL compared to rats fed the normal diet. HFD also increased serum glutamic-oxaloacetic transaminase (GOT), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP) and creatinine but decreased serum albumin and total protein. Administration of E. japonica seed, leaf, or fruit extract significantly decreased body weight, TC, TGs, LDL, VLDL, glucose, liver, and renal enzymes but increased HDL, albumin, and total protein levels. Conclusion: E. japonica seed, leaf, and fruit ethanol extract regulates body weight gain, has hypolipidemic properties, and positively affects liver and kidney enzymes.
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The interaction of TRPV1 and lipids: Insights into lipid metabolism. Front Physiol 2022; 13:1066023. [PMID: 36589466 PMCID: PMC9797668 DOI: 10.3389/fphys.2022.1066023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022] Open
Abstract
Transient receptor potential vanilloid 1 (TRPV1), a non-selective ligand-gated cation channel with high permeability for Ca2+, has received considerable attention as potential therapeutic target for the treatment of several disorders including pain, inflammation, and hyperlipidemia. In particular, TRPV1 regulates lipid metabolism by mechanisms that are not completely understood. Interestingly, TRPV1 and lipids regulate each other in a reciprocal and complex manner. This review surveyed the recent literature dealing with the role of TRPV1 in the hyperlipidemia-associated metabolic syndrome. Besides TRPV1 structure, molecular mechanisms underlying the regulatory effect of TRPV1 on lipid metabolism such as the involvement of uncoupling proteins (UCPs), ATP-binding cassette (ABC) transporters, peroxisome proliferation-activated receptors (PPAR), sterol responsive element binding protein (SREBP), and hypoxia have been discussed. Additionally, this review extends our understanding of the lipid-dependent modulation of TRPV1 activity through affecting both the gating and the expression of TRPV1. The regulatory role of different classes of lipids such as phosphatidylinositol (PI), cholesterol, estrogen, and oleoylethanolamide (OEA), on TRPV1 has also been addressed.
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Eugenol Reduces LDL Cholesterol and Hepatic Steatosis in Hypercholesterolemic Rats by Modulating TRPV1 Receptor. Sci Rep 2019; 9:14003. [PMID: 31570745 PMCID: PMC6768860 DOI: 10.1038/s41598-019-50352-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/11/2019] [Indexed: 01/09/2023] Open
Abstract
Eugenol, a component of essential oils of medicinal and food plants, has a hypolipidemic effect in experimental animals although its mechanism of action is still unclear. This study aims to explore the mechanism of the hypolipidemic effect of eugenol in rats fed a high cholesterol and fat diet (HCFD). Eugenol significantly reduced total cholesterol (TC), low-density lipoproteins (LDL), atherogenic index (AI) but not high-density lipoproteins (HDL) or triglycerides (TG). Eugenol also decreased steatosis and hepatic inflammation in liver sections, decreased hepatomegaly, and the hepatic marker enzymes alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activity and increased the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity in hypercholesterolemic rats. Eugenol did not inhibit hepatic 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase but caused down-regulation of transient receptor potential vanilloid (TRPV1) channels in the liver. Docking simulation using fast, rigid exhaustive docking (FRED) software indicated a tail-up/head-down interaction of eugenol with TRPV1 channel. Data indicate that eugenol does not inhibit HMG-CoA reductase but rather induces its action by interaction with TRPV1 channels.
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Chemical constituents of Fumaria densiflora and the effects of some isolated spirobenzylisoquinoline alkaloids on murine isolated ileum and perfused heart. Nat Prod Res 2019; 34:1180-1185. [PMID: 30773909 DOI: 10.1080/14786419.2018.1550761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Twenty-two alkaloids, were isolated from Fumaria densiflora. Two of these alkaloids, N-methyl-5-hydroxystylopine chloride and fumaricine N-oxide, were isolated for the first time from natural sources. Parfumine and fumaritine, in concentrations ranging from 3 × 10-7 to 9 × 10-4 M, caused concentration-dependent relaxation of ileum longitudinal segment. Also, parfumine and fumaritine in concentrations ranging from 3 × 10-4 to 9 × 10-2 M, caused concentration - dependent decrease in heart rate of the isolated perfused heart. A concentration of parfumine of 3 × 10-2 M increased but a higher concentration (9 × 10-2 M) decreased the amplitude of contraction of the isolated perfused heart. On the other hand, fumaritine, in concentrations ranging from 3 × 10-4 to 3 × 10-2 M, caused concentration - dependent increase, but a higher concentration (9 × 10-2 M) caused a decrease in the amplitude of contraction of the isolated perfused heart.[Formula: see text].
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Hypocholesterolemic effect of β-caryophyllene in rats fed cholesterol and fat enriched diet. J Clin Biochem Nutr 2018; 62:230-237. [PMID: 29892161 PMCID: PMC5990408 DOI: 10.3164/jcbn.17-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 11/06/2017] [Indexed: 12/21/2022] Open
Abstract
Hypercholesterolemia is a major risk factor for cardiovascular diseases. This study investigated the cholesterol-lowering potential of β-caryophyllene in a rat model. Hypercholesterolemia was induced by feeding male Wistar rats a high cholesterol and fat diet for 2 weeks. This was followed by oral administration of β-caryophyllene to hypercholesterolemic rats at 30, 100 and 300 mg/kg b.w. for 4 weeks. A dose of 30 mg/kg of β-caryophyllene significantly lowered serum total cholesterol, low density lipoprotein and the atherogenic index and significantly increased high density lipoprotein level. Moreover, it ameliorated liver injury as evidenced by decreasing hepatomegaly, macrovesicular steatosis and the activity of hepatic marker enzymes alanine aminotransferase and aspartate aminotransferase. Furthermore, it increased the activity of the antioxidant enzyme superoxide dismutase. This dose of β-caryophyllene significantly inhibited the activity of hepatic hydroxy-methylglutaryl coenzyme A reductase. Higher doses (100 and 300 mg/kg) of β-caryophyllene, however, did not induce significant beneficial effects on the studied parameters. These observations demonstrate that β-caryophyllene has a cholesterol-lowering effect on hypercholesterolemic rats, thus offering protection against hypercholesterolemia-induced diseases such as atherosclerosis and fatty liver.
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Anti-Obesity and Antihyperglycemic Effects of <i>Crataegus aronia</i> Extracts: <i>In Vitro</i> and <i>in Vivo</i> Evaluations. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/fns.2013.49126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Evaluation of the hypocholesterolemic effect and phytochemical screening of the hydroethanolic extract of Crataegus aronia from Jordan. Nat Prod Commun 2012; 7:35-38. [PMID: 22428238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
Chemical screening of the leaves and flowers of Crataegus aronia resulted in the isolation of hyperoside, quercetin, rutin and beta-sitosterol for the first time from this plant. The effects of the hydroethanolic extract of C. aronia (CAHE) on hypercholesterolemic rats were investigated. The rats, treated orally for four weeks with 400 mg/kg/day CAHE, exhibited significant decreases in serum total cholesterol (TC) and low-density lipoprotein (LDL). The results were compared with those obtained after oral administration of atorvastatin (10 mg/kg/day). Furthermore, 10-week daily co-administration of a high cholesterol diet and CAHE (200 mg/kg/day) prevented the increase in TC and LDL. These observations indicate that CAHE has a hypocholesterolemic effect.
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Evaluation of the Hypocholesterolemic Effect and Phytochemical Screening of the Hydroethanolic Extract of Crataegus Aronia from Jordan. Nat Prod Commun 2012. [DOI: 10.1177/1934578x1200700113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Chemical screening of the leaves and flowers of Crataegus aronia resulted in the isolation of hyperoside, quercetin, rutin and β-sitosterol for the first time from this plant. The effects of the hydroethanolic extract of C. aronia (CAHE) on hypercholesterolemic rats were investigated. The rats, treated orally for four weeks with 400 mg/kg/day CAHE, exhibited significant decreases in serum total cholesterol (TC) and low-density lipoprotein (LDL). The results were compared with those obtained after oral administration of atorvastatin (10 mg/kg/day). Furthermore, 10-week daily co-administration of a high cholesterol diet and CAHE (200 mg/kg/day) prevented the increase in TC and LDL. These observations indicate that CAHE has a hypocholesterolemic effect.
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The antinociceptive and anti-inflammatory effects of Salvia officinalis leaf aqueous and butanol extracts. PHARMACEUTICAL BIOLOGY 2010; 48:1149-1156. [PMID: 20860437 DOI: 10.3109/13880200903530763] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
CONTEXT The leaf of sage Salvia officinalis L. (Lamiaceae) is reputed in the folk medicine of Arabia, and Jordan in particular, to relieve pain associated with gastrointestinal disturbance. OBJECTIVES Evaluation of the antinociceptive and anti-inflammatory activities of aqueous and butanol extracts of S. officinalis leaf. MATERIALS AND METHODS The analgesic effects of the aqueous extract (10, 31.6, 100, 316, 1000 mg/kg) and butanol extract (10, 31.6, 100, 316 mg/kg) were studied using the hot-plate test for mice and the formalin-induced paw licking in rats. The effects were compared to those of morphine and the influence of naloxone on these effects was also evaluated. The same concentrations of both extracts were used to evaluate their anti-inflammatory effects using the cotton pellet granuloma and carrageenan-induced paw edema in rats. RESULTS The aqueous extract (10, 31.6, 100, 316, 1000 mg/kg) and butanol extract (10, 31.6, 100, 316 mg/kg) caused analgesic effect in the hot-plate latency assay as well as in early and late phases of formalin-induced paw licking in rats. These effects were reduced by the opioid receptor antagonist, naloxone (5 mg/kg). The same range of doses of both extracts caused dose-dependent inhibition of carrageenan-induced paw edema in rats as well as inhibition of cotton pellet granuloma. DISCUSSION AND CONCLUSION These observations suggest that the sage leaf aqueous and butanol extracts have analgesic and anti-inflammatory effects, confirming the traditional use of this plant for pain alleviation.
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Effects of selected flavonoids on deformability, osmotic fragility and aggregation of human erythrocytes. Clin Hemorheol Microcirc 1998; 18:165-73. [PMID: 9699038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The effects of 8 selected flavonoids of deformability, osmotic fragility and dextran-induced aggregation of human erythrocytes were studied. The following flavonoids were found to protect against loss of filterability (deformability) through 5 microns diameter pores of erythrocytes dehydrated with calcium ionophore A23187 (1.9 mumol/l): apigenin > quercetin > cirsimaritin > rutin > luteolin > chrysoeriol-4'-O-glucoside > 3,5,7-trihydroxy 4'-methoxy flavone 7-rutinoside, whereas beta-naphtho flavone enhanced the loss of filterability. When the potassium ionophore valinomycin (18 mumol/l) was used to induce cell dehydration, the order of potency of the flavonoids in protecting against loss of filterability was apigenin > cirsimaritin = chrysoeriol-4'-O-glucoside > 3,5,7-trihydroxy 4'-methoxy flavone 7-rutinoside > luteolin = rutin > quercetin, whereas beta-naphtho flavone again enhanced the loss of filterability. All flavonoids reduced ESR measured over 1 h except for 3,5,7-trihydroxy 4'-methoxy flavone 7-rutinoside which showed no effect, and for quercetin which significantly enhanced ESR. All flavonoids also improved erythrocyte osmotic fragility except for apigenin which significantly increased osmotic fragility. These effects were explained in terms of the number and location of hydroxyl groups on the basic skeleton of flavone. The results suggest that the presence of an OH and C5 is essential for the described rheological effects of these flavonoids.
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Pharmacological effects of selected flavonoids on rat isolated ileum: structure-activity relationship. GENERAL PHARMACOLOGY 1997; 28:767-71. [PMID: 9184817 DOI: 10.1016/s0306-3623(96)00299-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
1. Eleven selected flavonoids were studied to evaluate their effects on the rat isolated ileum and to determine their structure-activity relationships. 2. The flavonoids rutin and 3',5,7-trihydroxy-4' methoxyflavone-7-rutinoside, which have a sugar moiety (O-rha-glu), had no significant effect on the ileum, indicating that the presence of sugar substitution reduces the biological activity of the flavonoids. 3. Nine other flavonoids caused inhibition of tonic and phasic contractions of the ileum with the following order of potency from highest to lowest: galangin, quercetin, chrysin, xanthomicrol, flavone, naringenin, fisetin, morin, and flavanone. 4. Flavones were more potent than flavanones, indicating that the double bond at carbon 2-3 increases the potency of the flavonoid. 5. Galangin, quercetin, chrysin, and xanthomicrol, which have hydroxyl substituents on carbon 3 and/or 5, showed higher potency than flavone, indicating that such hydroxyl groups are essential for the activity. 6. Galangin was more potent than quercetin, morin, and fisetin, suggesting that the hydroxyl substituents on ring B attenuate the potency. 7. Quercetin caused more potent relaxation of the ileum than morin, suggesting that the presence of a hydroxyl group at C-2' of ring B attenuates the myolytic activity.
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Effects of hypoxia, mechanical and chemical endothelium denudation on guinea-pig isolated pulmonary arteries. GENERAL PHARMACOLOGY 1995; 26:113-22. [PMID: 7713350 DOI: 10.1016/0306-3623(94)00165-j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. The isolated unstimulated main trunk, extralobar and intralobar branches of the pulmonary artery of the guinea-pig developed well-sustained contractions upon exposure to hypoxia (95% N2-5% CO2 gas mixture; PO2 11-15 mm Hg). The contractions were readily reversible by reoxygenation (95% O2-5% CO2). 2. Mechanical removal of the endothelium did not significantly affect the magnitude of the hypoxia-induced contractions in rings obtained from the main trunk of the pulmonary artery but reduced those of rings obtained from the proximal and distal extralobar branches. 3. Mechanical removal of the endothelium also did not affect the magnitude of contractions induced by BaCl2 in the main but significantly reduced contractions induced by the same agent in the proximal and distal extralobar branches of the pulmonary artery, suggesting that the reduction of hypoxia-induced contractions in the endothelium-denuded rings is due to impairment of vascular reactivity. 4. Pretreatment with L-N-nitro arginine, an inhibitor of the synthesis of the endothelium-derived relaxing factor, did not significantly affect the hypoxia-induced contractions but increased the magnitude of BaCl2-induced contractions in the main and the extralobar branches. 5. These observations demonstrate that isolated pulmonary artery rings of the guinea-pig develop slow contractions in response to hypoxia without prior contraction with an agonist, and that the endothelium plays little role in the hypoxia-induced contractions of guinea-pig isolated large pulmonary arteries. 6. Furthermore, these observations suggest that the effect of mechanical endothelium denudation or pharmacological manipulation, such as EDRF inhibition, on vascular reactivity should be considered when the effect of hypoxia is studied in isolated pulmonary arteries.
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Abstract
Although ketamine increases pulmonary vascular resistance of patients, an occasional decrease of resistance in animals and humans has been reported. In addition, ketamine has a direct relaxant effect on isolated smooth muscle. The effects of ketamine on the main pulmonary artery rings isolated from the guinea pig were studied to elucidate the underlying mechanism of the reported relaxant effect of this anesthetic on smooth muscle. Ketamine (10-250 micrograms/mL) caused a concentration-dependent shift to the right of CaCl2 concentration-effect curves on artery rings, suggesting an interference with Ca2+ metabolism. In Ca(2+)-free buffer, ketamine (10-250 micrograms/mL) did not affect the magnitude of epinephrine-induced contractions but inhibited dose-dependent BaCl2-induced contractions. These observations suggest that ketamine inhibits transmembrane Ca2+ influx but does not affect its release from intracellular stores or its binding to intracellular receptor sites on the contractile system. Ketamine (25-500 micrograms/mL) also caused equipotent concentration-dependent relaxation of epinephrine-induced contractions in the absence and the presence of monensin, a Na(+)-ionophore that dissipates the Na+ gradient across the cell membrane, and in Na(+)-free, sucrose-substituted buffer. Ketamine (25-500 micrograms/mL) also relaxed ouabain-induced contractions to the baseline, an effect that was significantly attenuated in the presence of ruthenium red, a Ca2+ adenosine triphosphatase (ATPase) inhibitor. The relaxant effect of ketamine (250-750 micrograms/mL) of epinephrine-induced contraction also was attenuated in the presence of 0.1 mM lanthanum chloride (La3+), an inhibitor of adenosine 5'-triphosphate (ATP)-dependent Ca2+ extrusion, and completely inhibited in the presence of 10 mM La3+.(ABSTRACT TRUNCATED AT 250 WORDS)
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