Effects of crinum glaucum aqueous extract on intestinal smooth muscle activity

Crinum glaucum aqueous extract (1–8 mg/mL) produced a concentration dependent, non-competitive inhibition of contractions induced by acetylcholine (1.1 × 10⁻⁸–3.3 × 10⁻⁷M ) and calcium chloride (CaCl₂, 0.05–2 mM ) on the rat duodenum. Contractions of the guinea-pig ileum induced by acetylcholine (1.1 × 10⁻⁸–3.3 × 10⁻⁷M ) and histamine (1.1 × 10⁻⁸–3.3 × 10⁻⁷M ) were inhibited by the extract (1–4 mg/mL). The extract (0.125–2.0 mg/mL) also, produced a concentration dependent relaxation of the guinea-pig taenia coli, precontracted with potassium chloride (40 mM ). It is concluded that the extract is a non-specific relaxant of the gastrointestinal smooth muscles used. © 1998 John Wiley & Sons, Ltd.     

Pharmacological activity of the extracts of two Satureja obovata varieties on isolated smooth muscle preparations

Aqueous extracts of two varieties of Satureja obovata Lag. subsp. obovata: var. valentina and var. obovata, exhibited a dose-dependent inhibitory effect on the contractions induced by acetylcholine (Ach) (3.4 × 10^?8?6.8 × 10^?5M) and CaCl₂ (2 × 10^?4?1.28 ? 10^?2M) in rat duodenum and by noradrenaline (NA) (10^?9?5.12 × 10^?7 M) and CaCl₂ (2 × 10^?4?1.28 × 10^?2 M) in rat aorta. The extracts also produced relaxant effects in both tissue preparations precontracted with K⁺ (75 mM) and in rat aorta precontracted with NA (10^?6 M). Vasodilatory effects of the two extracts were attenuated when the endothelium was removed. The inhibitory effects of var. valentina were stronger. These results indicated a smooth muscle relaxant effect that could account for the use of these extracts in traditional medicine.     

Inhibitory effects of Cistus populifolius on contractile responses in the isolated rat duodenum

The medicinal plant Cistus populifolius L., shows an important dose-dependent spasmolytic activity. The ability of the Cistus extract to inhibit both acetylcholine (ACh) (3.4 × 10⁻⁸–6.8 × 10⁻⁵ M) and CaCl₂ (2 × 10⁻⁴–1.28 × 10⁻² M) -induced contractions and the relaxing effect on K⁺ (75 mM) -induced contractions may indicate a non-specific receptor antagonist. However, this action may be related to the influx of extracellular Ca²⁺. These antispasmodic effects are partly consistent with the use of C. populifolius in folk medicine for certain gastrointestinal disorders.     

Vascular action of the crude hydroalcoholic extract from Hymenaea martiana on the isolated rat and rabbit aorta

The present study investigates the effect of the hydroalcoholic extract (HE) from Hymenaea martiana (Leguminosae) on endothelium-dependent and independent relaxation responses induced by acetylcholine (ACh), histamine (His), calcium ionophore (A23187) and sodium nitroprusside in precontracted aortic rings from rat and rabbit. In addition, we have also evaluated the action of the HE on noradrenaline- (NA), angiotensin I-(AI) and AII-induced contractions in the rabbit aorta. The HE (0.25–0.5 mg/mL) inhibited in a concentration-dependent manner the relaxant response induced by ACh in rings of rabbit aorta and by His in rat aorta. Relaxation in response to A23187 was inhibited in rat but not in rabbit aortic rings. In contrast, the HE was completely ineffective against endothelium-independent relaxations caused/by sodium nitroprusside in rabbit aorta rings. The HE (0.5–1.0 mg/mL) significantly enhanced the maximal contractile responses induced by NA in rabbit aorta set up with the endothelium, but caused no effect in endothelium rubbed preparations. In addition, the HE (0.5 mg/mL) markedly antagonized the contractile responses elicited by AI, but caused only a slight effect on AII-induced contractile responses in rabbit aorta. These findings indicate that the active principle(s) present in the HE from the bark of Hymenaea martiana selectively inhibit the endothelium-dependent vasorelaxant responses caused by several substances in aortic rings from rat and rabbit, presumably by a mechanism related with endothelium-derived relaxation factor synthesis and/or inactivation. The HE also antagonized AI but not AII-induced contractions in rabbit aorta, suggesting some interference with the angiotensin converting enzyme.     

Inhibition of Histamine-induced Contraction of Rat Ileum by Promethazine and the Methanol Stembark Extract of Erythrina sigmoidea (Hua)

Histamine, a potent H₁ and H₂ receptor agonist provoked dose dependent contractions of the rat ileal strip. The contractile effect was reduced by almost 54.6% when challenged with 1.8 μg/mL of the stembark extract of Erythrina sigmoidea (ES) while 4.8 μg/mL of the plant extract completely abolished 10⁻⁴ Msc histamine-induced contraction. A similar relaxant effect was obtained with 0.5 μg/mL promethazine, a potent H₁ blocker, but this relaxant effect was less significant compared with that of the plant extract.     

Pharmacological studies of Striga senegalensis Benth (Scrophulariaceae) as an abortifacient

The methanol extract of Striga senegalensis Benth (Scrophulariaceae) was investigated on isolated rat uterus. Acetylcholine and the methanol extract of the plant produced dose related contractions of smooth muscle of the isolated rat uterus in vitro. Atropine in doses of 2 × 10⁻² to 32 × 10⁻² μg/mL antagonized dose dependently the contraction of the isolated rat uterus produced by both acetylcholine (1.6 × 10⁻¹ μg/mL) and the methanol extract (160 μg/mL). © 1998 John Wiley & Sons, Ltd.     

Different Effects of Some Isoquinoline Alkaloids from Argemone mexicana on Electrically Induced Contractions of Isolated Guinea-pig Ileum

The present study examines the effects of the extracts [petroleum ether, CHCl₃, CHCl₃/MeOH (9:1) and MeOH], partially purified fractions and pure compounds from Argemone mexicana on the electrically induced contractions of the isolated guinea-pig ileum (E.C.I.). The results of the experiments indicate that CHCl₃/MeOH (9:1) and MeOH extracts, tested at a concentration of 400, 200 and 100 μg/mL, dose-dependently reduced the guinea-pig ileum contractions, whereas the petroleum ether and CHCl₃ extracts did not affect it. Furthermore, the partially purified fractions II–V from the MeOH extract, each tested at concentrations of 200, 100 and 50 μg/mL also inhibited E.C.I. Finally the pure compounds 1–2 (5×10⁻⁶–1×10⁻⁵–5×10⁻⁵ M ) isolated and purified from the above fractions significantly reduced, in a dose dependent manner, the electrical contractions of the ileum, whereas compound 3 (5×10⁻⁶–1×10⁻⁵×10⁻⁵ M ) increased them. Since the active compounds 1–3 were respectively identified as protopine, allocryptopine and berberine by NMR, the observed effects could be related mainly to these compounds. © 1997 by John Wiley & Sons, Ltd.     

Inhibiting Activity of Some Glucoindolalkaloids and Iridoids from Sickingia williamsii on Electrically Induced Contractions of Isolated Guinea-pig Ileum

The present study examined the effects of the extracts (petroleum ether, CHCl₃, CHCl₃/MeOH (9:1) and MeOH), partially purified fractions and pure compounds (mainly alkaloids and iridoids) from Sickingia williamsii on the electrically induced contractions of the isolated guinea-pig ileum. The results of our experiments indicate that CHCl₃/MeOH (9:1) and CHCl₃ extracts, tested at concentrations of 300, 150 and 30 μg/mL, dose-dependently reduced the guinea-pig ileum electrical contractions, whereas MeOH and petroleum ether extracts did not affect it. Furthermore, both the partially purified fractions I–IV each tested at concentrations of 500, 250 and 100 μg/mL from the CHCl₃/MeOH (9:1) extract and some pure compounds (10⁻⁴ M , 5×10⁻⁵ M and 2.5×10⁻⁵ M ) isolated and purified from the above fractions significantly reduced, in a dose dependent manner, the electrical contractions of the ileum. As the active pure compounds possess an indole nucleus or/and an iridoid nucleus in their structures, the inhibitory effects appear to depend on these structures.     

Pharmacological Actions of Naringin on Alpha,Beta-adrenoceptors and Uptake of Noradrenaline in Rat Isolated Vas Deferens

In normal Krebs solution, naringin (1×10⁻⁷ M sc–2×10⁻⁶ M ) enhanced noradrenaline-induced contractions in rat isolated vas deferens increasing this potentiation in a concentration dependent manner. This enhancing effect continued in the presence of yohimbine (10⁻⁶ M ) or propranolol (10⁻⁶ M ). Naringin did not modify significantly the dopamine dose-response curves. In a medium containing 10⁻⁸ M prazosin, naringin decreased noradrenaline dose-response curves underneath the control curve at all the doses tested. Naringin did not modify significantly the NA dose-response curve in a medium containing cocaine (10⁻⁵ M ) or oestradiol (10⁻⁵ M ). The potentiation produced by naringin on the NA-induced contractions in rat vas deferens may be due to alpha-1 receptor activation, together with an interference of naringin in catecholamine uptake process.     

黄芩素对大鼠离体胸主动脉的舒张作用及其机制

目的:研究黄芩素(BAI)对去甲肾上腺素(NE,1×10-6mol· L-1)和氯化钾(KCl,6×10-2 mol·L-1)预收缩健康成年雄性大鼠胸主动脉环的舒张作用,并探讨其作用机制.方法:应用离体血管环技术观察BAI对大鼠胸主动脉环张力的作用,记录NE预收缩的离体大鼠胸主动脉环张力变化.采用一氧化氮合酶(eNOS)抑制剂L-硝基精氨酸甲酯(L-NAME,1×10-4mol·L-1)、环氧合酶抑制剂吲哚美辛(INDO,1×10-5mol· L-1)和鸟苷酸环化酶抑制剂亚甲蓝(MB,1×10-5mol· L-1)和不同的钾通道阻滞剂预孵后观察BAI对血管环张力改变的影响,并观察对NE诱发的内钙释放和CaCl2引起的外钙内流的影响.结果:BAI对NE或KCl预收缩的内皮完整和去内皮大鼠离体胸主动脉环均产生明显的舒张作用,与溶剂组相比差异有统计学意义.预先用L-NAME,MB,KV通道阻断剂四氨基吡啶(4-AP,1×10-4mol· L-1),KC.通道阻断剂四乙胺(TEA,1×10-3mol· L-1),Kir通道阻断剂氯化钡(BaCl2,1×10-4mol·L-1)孵育后,BAI对预收缩的血管张力的改变与无阻断药时比较,差异均无统计学意义;预先用KATP通道阻断剂格列苯脲(Gli,1×10-5mol·L-1)和INDO孵育后,BAI的舒张血管作用减弱,与无阻断药比较差异有统计学意义(P＜0.05);且BAI对NE外钙内流引起的收缩有明显的抑制作用.结论:黄芩素可明显降低由NE诱发的血管环张力的升高,且其作用具有浓度依赖性,此作用有内皮依赖性和非内皮依赖性的特点.内皮依赖性收缩可能与前列环素(PGI2)途径有关,非内皮依赖机制与KATP通道和钙离子通道有关.     

Xanthine Oxidase Inhibitory Activity of Flavonoids and Tannins from Hexachlamys edulis (Myrtaceae)

The acetone-water extract of Hexachlamys edulis (Myrtaceae) inhibited the enzyme xanthine oxidase (XO) in vitro . Bioassay-guided isolation led to the gallic acid ester in 2″ of myricitrin (desmanthin-1), (-)-epigallocatechin-3-O-gallate (EGG) and pentagalloylglucose as the main XO inhibitors of H. edulis . Desmanthin-1 and EGG were mixed-type inhibitors of XO with K _i values of 1.6×10⁻⁴ M and 1.8×10⁻⁴ M , respectively. Pentagalloylglucose was an uncompetitive XO inhibitor with a K _ESI of 6.7×10⁻⁶M . From the active n -butanol soluble part of the aqueous acetone extract of H. edulis , several flavonoids were isolated. The flavonoids were mainly myricetin-3-O-monoglycosides with the quercetin glycoside avicularin as a minor compound displaying a weak inhibitory activity towards XO.     

白藜芦醇对大鼠离体胸主动脉环的舒张作用

目的:观察白藜芦醇(resveratrol,RVL)对大鼠离体胸主动脉血管的舒张作用并探讨其机制。方法:采用离体血管环灌流方法,观察RVL在含Ca²⁺或无Ca²⁺ Krebs液孵育条件下对去甲肾上腺素(NA)引起的血管平滑肌收缩的影响;同法观察RVL对30,80mmol·L^-1的KCl引起的血管平滑肌收缩的影响;RVL对NA引起的依赖于细胞内钙和细胞外钙收缩反应的影响,以及加入N-G-硝基-L-精氨酸(L-NNA)和优降糖后RVL舒张大鼠离体主动脉环效应的变化。结果:RVL呈浓度依赖性舒张NA引起的血管收缩;无Ca²⁺ 组RVL抑制NA所致血管平滑肌收缩效应大于含Ca²⁺ 组;RVL能够拮抗NA诱发的依内钙的收缩反应,而对外钙收缩无抑制。RVL对80,30mmol·L^-1 的KCl引起的血管平滑肌收缩均有抑制作用,且前者量效曲线明显上移。L-NNA使RVL舒血管效应降低(26.0±4.6)%;优降糖组的血管舒张受抑程度与对照组无显著差别(P>0.05)。结论:RVL可呈内皮依赖性舒张血管平滑肌,其作用机制可能与该药促进NO合成释放,开放钙激活的钾通道以及抑制血管平滑肌细胞外钙内流和内钙释放有关。     

Biological Activity and Xanthine Oxidase Inhibitors from Scirpus californicus (C. A. Mey.) Steud.

The methanol extract of the rhizomes of Scirpus californicus (Cyperaceae) inhibited the enzyme xanthine oxidase (XO) in vitro . Bioassay-guided isolation led to piceatannol, scirpusin A and scirpusin B as the main XO inhibitors of S. californicus. Piceatannol, scirpusin A and B were mixed-type inhibitors of the XO with K _i values of 1.1×10⁻⁴, 6×10⁻⁴ and 5×10⁻⁵ M , respectively. The extract and above mentioned compounds were marginally active as hypotensors when tested in normotensive rats at 2.5 mg/kg and were inactive towards the DNA binding assay in vitro.     

Vasorelaxant effects of extracts of the stem bark of Terminalia superba Engler & Diels (Combretaceae)

Aim of the study

The stem bark of Terminalia superba (Combretaceae) (TS) is used in traditional Cameroonian medicine as antihypertensive remedy. In the present study, we investigated the vasorelaxant properties of different extracts of TS and their underlying mechanisms.

Materials and methods

Activities of aqueous (AQU), methanolic (MET), methylene chloride (MC), and methylene chloride–methanol (MCM) extracts of TS were evaluated on isolated rat aortic rings precontracted with phenylephrine (PE) or high KCl.

Results

All extracts induced a vasodilating effect both on KCl- and PE-induced contractions. The effects of MC and MCM extracts were greater than those of AQU or MET extracts (P < 0.05). MC had an endothelium-independent effect and reduced Ca⁺⁺-induced contraction following PE or KCl challenge (P < 0.05). After incubation with verapamil, MC induced a relaxation in rings precontracted by PE (P < 0.001). By contrast, the effect of MCM was endothelium-dependent and decreased by the nitric oxide synthase inhibitor N_W-nitro-l-arginine methyl ester (P < 0.05).

Conclusions

These data demonstrate that the MC extract exhibits vasorelaxant effects that are partly due to inhibition of extracellular Ca⁺⁺ influx and/or inhibition of intracellular Ca⁺⁺ release in vascular smooth muscle cells. By contrast, the effect of the MCM extract was found to be endothelium- and nitric oxide dependent.     

Pharmacological actions of the gut active principles in Croton penduliflorus hutch. Seed on isolated smooth and skeletal muscles and on blood pressure

The effects of Croton penduliflorus seed crystals (CP crystals) were investigated on isolated guinea-pig ileum, chick biventer cervicis muscle and frog rectus abdominis muscle. The effect of the crystals on flood pressure of normotensive Sprague Dawley rats was also investigated. CP crystals induced concentrations-dependent contractions in the guinea-pig ileum with EC₅₀ of 2.39 × 10⁶ g/mL. Contractions induced by CP crystals in the guinea-pig ileum were not inhibited by atropine (2 × 10^?7-1.2 × 10^?6 g/mL), tetrodotoxin (3 × 10^?8-2 × 10^?7 g/mL), hexamethonium (7 × 10^?6-2.8 × 10^?5 g/mL), mepyramine (2 × 10^?7 g/mL) and noradrenaline (2 × 10^?5 g/mL) but were completely (100%) inhibited by indomethacin (7.2 × 10^?6 g/mL). CP crystals (1.0 × 10^?6-5.0 × 10^?4 g/mL) could not elicit contractions in either chick biventer cervicis or frog rectus abdominis muscle. The mean blood pressure of normotensive Sprague Dawley rats was significantly reduced by CP crystals (1.6 × 10^?4-2.5 × 10^?3 g/mL) while the heart rate was significantly reduced by an intravenous infusion of the crystals (2.5 × 10^?3 g/kg) after 2min. The methods employed and the significance of the results obtained are discussed.     

Herbal medicine Catuama induces endothelium-dependent and -independent vasorelaxant action on isolated vessels from rats,guinea-pigs and rabbits

The present study was designed to examine the vasorelaxant action of the herbal medicine Catuama and the hydroalcoholic extracts (HE) of each plant present in this product and to compare their effects with that caused by acetylcholine (ACh) in intact (⁺E) or in endothelium-rubbed (⁻E) rings of rat thoracic aorta (RA), guinea-pig pulmonary artery (GPPA), guinea-pig mesenteric artery (GPMA), rabbit pulmonary artery (RPA), rabbit mesenteric artery (RMA) precontracted with noradrenaline (NA) or phenylephrine (PE). The extract of Catuama (1-3000 μg/mL) produced graded relaxation of RA, ⁺E or ⁻E, with mean EC₅₀ of 430 μg/mL and ≊ 3000 μg/mL and E_max of 81 % ± 15 % and 47% ± 4 %, respectively. The nitric oxide (NO) synthase inhibitor, N^ω-nitro-L -arginine (L -NOARG, 100 μM ), inhibited in vasorelaxant action (p < 0.05) in RA (⁺E), while indomethacin (3 μM ), propranolol (1 μM ), glibenclamide (1 μM ), methylene blue (10 μM ) and apamin (0.1 μM ) had no significant effect. ACh (1-1000 μM ) caused graded relaxation in RA with ⁺E, these effects being markedly antagonized by L -NOARG (100 μM ), methylene blue (10 μM ) and partially by apamin (0.1 μM ), but not by indomethacin (3 μM ), glibenclamide (1 μM ) or propranolol (1 μM ). The Catuama extract (1-3000 μg/mL) produces partial relaxations in rings of RMA (mean EC₅₀ of 1073 μg7/ml and E_max of 56 % ± 13 %), an effect which was antagonized by L -NOARG (100 μM ). In RPA (⁺E) the extract produces partial relaxation followed by contraction (E_max 28 % ± 6 %), an effect which was abolished by L -NOARG (100 μM ) or methylene blue (10 μM ). The extract caused graded relaxation in rings of GPPA and GPMA with mean EC₅₀ values of 60 μg/mL and 1148 μg/mL and E_max 96% ± 2% and 88% ± 12%, respectively. L -NOARG (100 μM ) blocked the Catuama extract vasorelaxation in GPPA and only partially in GPMA, but markedly antagonized the vasorelaxations caused by ACh in both GPPA andRMA. The HE Paullinea cupana, Zinziber officinalis and Trichilia catigua (1-3000 μg/mL) caused a graded vasorelaxant effect ⁺E of RA with a mean EC₅₀ of 22, 55 and 1793 μg/mL and E_max 100%, 86% ± 7% 70% ± 2%, respectively. In addition the HE of P. cupana also caused graded relaxation in ⁻E of RA with EC₅₀ and E_max of 233 μg/mL and 100%, respectively, while T. catigua and Z. officinalis produced partial relaxation in RA ⁺E. In contrast the HE of Ptychopetalum olacoides caused little contraction (46% ± 14%). These results demonstrate that the medicinal herb Catuama produces significant vasorelaxation responses in vessels from different animal species, and show that its effects are in great part dependent on the release of NO or NO-derived substances. Our results also demonstrate that the vasorelaxant action of the product Catuama seems to be due to the action of the active principles present mainly in P. cupana; T. catigua and, to a lesser extent, in Z. officinalis. Such results may contribute to the explanation of its beneficial effect of Catuama herbal medicine in the management of cardiovascular disturbances. © 1997 John Wiley & Sons, Ltd.     

Effect of CYSTUS052® and green tea on subjective symptoms in patients with infection of the upper respiratory tract

Examples of medicinal herbs that have been perpetuated along several generations based simply on a folk tradition are Cistus and green tea. The principal active constituents of the genus Cistus and green tea are polyphenolic compounds. Polyphenols exhibit a wide range of antibacterial, antifungal and antiinflammatory effects. The present work aimed to investigate the clinical effect of a Cistus extract (CYSTUS052^®) in comparison with green tea on 300 patients with infections of the upper respiratory tract. Due to the lack of clinical study data on their efficacy in patients, this is a report of the findings of our study on the clinical efficacy of CYSTUS052^® in patients with the upper respiratory tract infections (URTIs). This study observed a total of 300 patients (277 completers) treated with CYSTUS052^® given in lozenges compared with treatment with an extract of green tea. The patients scored the subjective severity of target symptoms using a predefined scale. The score of subjective symptoms decreased over the course of treatment with CYSTUS052^®, whereas treatment with green tea resulted in a less significant decrease of symptoms. CYSTUS052^® therefore proved to be an effective adjuvant for the treatment of respiratory infections. Copyright © 2009 John Wiley & Sons, Ltd.     

天麻素对离体大鼠胸主动脉环的舒张作用及其机制

目的:研究天麻素对离体大鼠胸主动脉环的舒张作用并探讨其可能的机制。方法:记录去甲肾上腺素(NE)和KCl预收缩的离体大鼠主动脉环张力变化,观察天麻素的舒血管作用及不同工具药对其作用的影响。结果:天麻素对去甲肾上腺素(NE,1×10-6mol.L-1)和KCl(6×10-2mol.L-1)引起的去内皮和内皮完整胸主动脉环的收缩均有舒张作用,二者没有显著差别;L-硝基精氨酸甲酯(L-NAME,1×10-4mol.L-1)、亚甲蓝(MB,1×10-5mol.L-1)、吲哚美辛(INDO,1×10-5mol.L-1)并不能抑制天麻素对胸主动脉环的舒张作用;钾离子通道阻断剂4-氨基吡啶(4-AP,1×10-4mol.L-1)、四乙基胺(TEA,1×10-3 mol.L-1)、格列苯脲(glibenclamide,1×10-5mol.L-1)、BaCl2(1×10-4mol.L-1)均能抑制天麻素对血管环的舒张作用;在无钙环境下,预孵育天麻素对去甲肾上腺素收缩有明显抑制作用。结论:天麻素有浓度依赖性的血管舒张作用,此作用不依赖血管内皮,与钾离子通道及抑制血管平滑肌细胞内质网储存钙的释放和外钙内流有关系。     

Effects on rat uterine and aorta strip smooth muscle of Thymus leptophyllus extract

The diethylether extract from Thymus leptophyllus was found to be more active on uterine smooth muscle than on aorta strips. Rat uterus experiments with and without extracellular calcium, yielded similar IC₅₀ values. A non-specific mechanism for the relaxant activity can therefore be postulated. In rat aorta and in the presence of extracellular calcium the extract inhibited the contractile response induced by K⁺ depolarizing solution and had a less inhibitory effect on noradrenaline (NA) contraction. In a Ca²⁺-free solution the extract strongly reduced the Ca²⁺-release induced by NA, but it did not affect the transient contraction caused by caffeine (CAF).     

金丝桃苷对大鼠离体大脑中动脉血管内皮功能的影响及其内在机制的研究

研究金丝桃苷(hyperoside, Hyp)对大鼠离体大脑中动脉(middle cerebral artery, MCA)血管内皮功能的影响, 探讨其可能存在的机制。采用动脉加压灌注法测定脑血管舒缩功能和细胞膜电位记录法测定血管平滑肌细胞膜静息电位, 观察Hyp(1×10~1×10 mol·L)对U46619(1×10 mol·L)预收缩大鼠MCA的作用。结果发现, 累加浓度的Hyp可诱导U46619预收缩大鼠离体MCA产生明显浓度依赖性的舒张作用和血管平滑肌细胞膜静息电位超极化反应, 其最大舒张率为(73.2±6.1)%, 最大超极化幅度为(-13.2±2.2) mV。去除血管内皮细胞后, Hyp仍有一定的舒张反应和超极化作用, 但其作用明显减弱, 与血管内皮完整组比较, 差异显著(P <0.01);在合用一氧化氮合酶(NOS)抑制剂L-NAME(3×10 mol·L)和前列环素(PGI₂)合成酶抑制剂Indo(1×10 mol·L)后, Hyp仍可介导大鼠MCA产生显著的舒张反应和超极化作用;1×10 mol·L Ca激活性钾通道(K_Ca)阻断剂TEA或1×10 mol·L胱硫醚-γ-裂解酶(CSE)抑制剂PPG可明显减弱Hyp诱导大鼠MCA产生的非NO非PGI₂样舒张作用和超极化反应;外源性硫化氢(H₂S)的供体NaHS(1×10~1×10 mol·L)或H₂S合酶(CSE)底物L-Cys(1×10~1×10 mol·L)可介导大鼠MCA产生一定的舒张作用和超极化反应。结果表明, Hyp可诱导大鼠MCA产生内皮依赖性和较弱的内皮非依赖性血管舒张作用和超极化作用, 其内皮依赖性舒张作用可能与Hyp促使MCA内皮细胞生成内源性H₂S增多, 继而激活K_Ca, 使K_Ca通道开放, 引起细胞膜超极化, 进而阻滞Ca内流, 从而产生舒张血管作用有关。