Biphasic Response of Mouse Ileal Smooth Muscles to Aspirin in a Dose Response Manner

Strips of mouse ileum were used in current study to investigate the effect of different concentrations of aspirin on their smooth muscles activities. Student＇s kymograph and glass jacket organ bath were used for recording ilum smooth muscles contractions. The recording of the muscles contractions showed regular autorhythmic pattern, and this contraction was enhanced by both ACh （acetylcholine） and KCI （potassium chloride）. This normal contraction and that induced by ACh and KCI mainly depended on the extracellular calcium in their tension and maintaining. Aspirin exerted different effects on ileal smooth muscles contractions depending upon concentrations. Low concentrations 2-40 mM had an stimulatory effects, while high concentrations 60-200 mM had an inhibitory effects, which led to relaxation. Ca^＋2 free solution abolished muscles response to aspirin with the concentrations caused contractions. Aspirin in tum led to continuation of acetylcholine induced contractions.

Relaxant Effects of Matrine on Aortic Smooth Muscles of Guinea Pigs

Objective To determine whether matrine, a kind of traditional Chinese medicinal alkaloid, can relax the aortic smooth muscles isolated from guinea pigs and to investigate the mechanism of its relaxant effects. Methods Phenylephrine or potassium chloride concentration-dependent relaxation response of aortic smooth muscles to matrine was studied in the precontracted guinea pigs. Results Matrine （1×10^-4 mol/L -3.3×10^-3 mol/L） relaxed the endothelium-denuded aortic rings pre-contracted sub-maximally with phenylephrine, in a concentration-dependent manner, and its pre-incubation （3.3× 10^- 3 mol/L） produced a significant rightward shift in the phenylephrine dose-response curve, but had no effects on the potassium chloride-induced contraction. The anti-contractile effect of matrine was not reduced by the highly selective ATP-dependent K^＋ channel blocker glibenclamide （10.5 mol/L）, either by the non-selective K^＋channel blocker tetraethylammonium （10^-3 mol/L）, or by the β-antagonist propranolol （10^-5 mol/L）. In either ＂normal＂ or ＂Ca^2＋-free＂ bathing medium, the phenylephrine-induced contraction was attenuated by matrine （3.3×10^-3 mol/L）, indicating that the vasorelaxation was due to inhibition of intracellular and extracellular Ca^2＋ mobilization. Conclusion Matrine inhibits phenylephrine-induced contractions by inhibiting activation of α-adrenoceptor and interfering with the release of intracellular Ca^2＋ and the influx of extracellular Ca^2＋.

Construction of human eukaryotic expression plasmid vascular endothelial growth factor 165 and its expression in transfected vascular smooth muscles

BACKGROUND: The highly specific vascular endothelialgrowth factor (VEGF) induces the growth of vascular en-dothelial cell. This study was to construct the eukaryoticexpression plasmid of vascular endothelial growth factorl65(VEGF165) and observe its expression in vascular smoothmuscles (VSMCs).METHODS: The primers were designed and synthesizedaccording to the gene sequences of human VEGF165. TheVEGF165 gene was obtained from umbilic artery tissue bythe method of RT-PCR, then it was cloned to eukaryoticexpression plasmid pBudCE4.1 by recombination strategy.The eukaryotic expression plasmid named pBudCE4.1/VEGF165 was identified by restriction enzyme digestion,and was sequenced. The pBudCE4.1/VEGF165 was trans-fected into VSMCs by using lipofection. The VEGF165 ex-pression of mRNA and protein was detected by RT-PCRand Western blot respectively.RESULTS: VEGF165 was shown about 576bp by RT-PCR.Sequencing revealed the amplified VEGF165 gene was iden-tical with that in the GeneBank. Restrictive enzyme (HindBam HI) digestion analysis showed that recombinantexpression plasmid pBudCE4. l/tVEGF165 had been con-structed successfully. The expression of VEGF165 at mRNAand protein levels in the transformed VSMCs had beendemonstrated by RT-PCR and Western blot.CONCLUSIONS: The recombinant eukaryotic expressionplasmid pBudCE4.1/VEGF165 has been successfully con-structed and expressed in transformed VSMCs. The presentstudy has laid a foundation for VEGF165 gene therapy ofvascular stenosis in the transplant organ.

Effects of Atractylodes Macrocephala on the Cytomembrane Ca^(2+)-activated K^+ Currents in Cells of Human Pregnant Myometrial Smooth Muscles

The study examined the inhibitory effect of Atractylodes macrocephala （AM） on the uterine contraction during premature delivery and explored its electrophysiological mechanism by studying the effects of AM on the Ca^2＋-activated K^＋ currents of pregnant human myometrial smooth muscle cells with or without the treatment with intedeukin-6. Single cells were acutely isolated from pregnant human myometrial smooth muscles. Whole-cell Ca^2＋-activated K^＋ currents were recorded by using an Axopatchl-D amplifier. The cells were divided into three groups： group A in which AM was added into perfusate, group B, in which interleukin-6 was added into perfusate） and group C in which AM was added into perfusate after addition of interleukin-6. IL-6 10 ng/mL inhibited BKca by 36.9%±13.7% as compared with control （P〈0.01）. AM at 2 mg/mL raised BKca by 36.7%±22.6% or 45.2%±13.7% with or without the treatment of IL-6, respectively （P〈0.01）. It is concluded that AM was able to enhance the BKca of pregnant human myometrial smooth muscle cells treated or untreated with interleukin-6 and its effect on the BKca IL-treated cells was stronger that its effect on BKca of untreated cells. Our results suggested that AM can help to maintain the membrane potentials and the resting status of pregnant human myometrial smooth muscle cells.

Influence of Angiotensin II on α1-Adrenergic Receptors Function in Rat Aorta and Expression in Vascular Smooth Muscle Cells

Angiotensin II (Ang II) is the main mediator of the Renin-Angiotensin-System acting on AT1 and other AT receptors. It is regarded as a pleiotropic agent that induces many actions, including functioning as a growth factor, and as a contractile hormone, among others. The aim of this work was to examine the impact of Ang II on the expression and function of α1-adrenergic receptors (α1-ARs) in cultured rat aorta, and aorta-derived smooth muscle cells. Isolated Wistar rat aorta was incubated for 24 h in DMEM at 37˚C, then subjected to isometric tension and to the action of added norepinephrine, in concentration-response curves. Ang II was added (1 × 10−5 M), and in some experiments, 5-Methylurapidil (α1A-AR antagonist), AH11110A (α1B-AR antagonist), or BMY-7378 (α1D-AR antagonist), were used to identify the α1-AR involved in the response. Desensitization of the contractile response to norepinephrine was observed due to incubation time, and by the Ang II action. α1D-AR was protected from desensitization by BMY-7378;while RS-100329 and prazosin partially mitigated desensitization. In another set of experiments, isolated aorta-derived smooth muscle cells were exposed to Ang II and α1-ARs proteins were evaluated. α1D-AR increased at 30 and 60 min post Ang II exposure, the α1A-AR diminished from 1 to 4 h, while α1B-AR remained unchanged over 24 h of Ang II exposure. Ang II induced an increase of α1D-AR at short times, and BMY-7378 protected α1D-AR from desensitization.

Effects of Ginkgo biloba extracts with mirodenafil on the relaxation of corpus cavernosal smooth muscle and the potassium channel activity of corporal smooth muscle cells

In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.

Relaxation of rabbit cavernous smooth muscle to 17β-estradiol: a non-genomic, NO-independent mechanism

Aim: To investigate whether estrogen was involved in relaxation of rabbit cavernous smooth muscle. Methods: Relaxation response of the rabbit cavernous smooth muscles to 17β-estradiol (0.3, 3, 30 and 300 nmol/L) were observed in vitro. The response of the muscle strips to estrogen after incubation with either actinomycin D (10μmol/L) or L-NAME (10μmol/L) were also evaluated. Inside-out mode of patch clamp in a single smooth muscle cell was applied to investigate the Maxi-K channel activities. Results: Estrogen caused a dose-dependent relaxation of the strips precontracted with norepinephrine. The maximal response was noted about 10 minutes after treatment. The estrogen-induced relaxation was prevented by neither actinomycin D nor L-NAME, suggesting that the response was not mediated by gene transcription or nitric oxide (NO). Application of 17β-estradiol increased the Maxi-K channel activities. Conclusion: 17β-estradiol may be involved in relaxation of rabbit cavernous smooth muscles via a non genomic and NO independent mechanism. 17β-estradiol stimulates Maxi-K channel of the rabbit cavernous myocyte.

Morphological Characteristics of Smooth Muscle Cells Isolated from the Rat Ductus Deferens

The aim of this study was to establish a method of isolating and culturing smooth muscle cells from the ductus deferens of rats. Smooth muscle cells were prepared from ductus deferens by explanting technique after dissection of adventitia and intimae, and cultured in vitro. The identification of the smooth muscle cells were verified by using anti u-smooth muscle actin （a-SMA） immunohistochemistry studies. The result suggested that the cells are multi-morphous, showing long fusiform or star shapes. The apophysis of cells contacted and coalesced to each other, in some regions the cells overlapped in multilayer, while in the other regions they formed monolayer that fluctuated and showed a ＂peak-valley＂ shape. They presented a positive reaction through immunohistochemistry studies. The purity of the cells was more than 99% through this method. The culturing of smooth muscle cells by explanting technique is simple and stable.

Arsenic trioxide inhibites transgenic tumor necrosis factor-α promoter activity in vascular smooth muscle cells and THP-1 monocytes in vitro

Aim This study was to evaluate the effect of arsenic trioxide （As2O3） on the transgenic TNF-α promoter activity in cultured vascular smooth muscle cells （VSMCs） and THP-1 monocytes. Methods Human TNF-α promoter was constructed by reporter gene system and was transiently transfected into VSMCs and THP-1 in vitro. The promoter activity was tested by luciferase activity with or without LPS and Ang Ⅱ stimulation, before and after different dosage of As2O3 treatment. Results 1. TNF-α promoter effectively expressed in VSMCs and THP-1 compared with CMV promoter （58.3% and 80.9%, respectively）. Both LPS and Ang Ⅱ significantly up-regulated TNF-α promoter activity （P〈0.05）. 2. As2O3 significantly inhibited, both intact and LPS/Ang Ⅱ stimulated promoter activity, in a dose dependent manner （P〈0.05）, and in both cell type. Conclusion These results manifested that, the inhibition effect of As2O3 on the activity of human TNF-α promoter indicated its potential inhibition on pro-inflammatory cytokine genes expression at transcriptional level and its potential anti-inflammatory property in the cardiovascular system.

Inhibitory Effects of Sodium Ferulate on Proliferation of Rabbit Aortic Smooth Muscle Cells Induced by Oxidized LDL

The effects of sodium ferulate(SF), a water-soluble element of Chinese medicine Angelica sinensis diels, on cell-mediated oxidative modification of human low density lipoprotein(LDL) and proliferation of rabbit aortic smooth muscle cells(SMCs) were investigated. Using experimental models of proliferation of cultured rabbit aortic SMCs induced by oxidized LDL(ox-LDL), the extent of oxidation was determined by thiobarbituric acid reactive substances(TBARS) method, MTT colorimetry and 3H-thymidine(3H-TdR) incorporation were used to observe proliferation of SMCs. It showed that SF effectively inhibited cell-mediated oxidation induced by Cu2+ in a concentration-dependent manner. At the final concentration of 40, 80, 120 gmL-1, SF could significantly inhibit 3H-TdR incorporation and cell Proliferation in a dose-dependent manner. The results indicated that SF could, in vitro protect LDL against oxidative modification and inhibit the proliferation of SMC, which might be due to its free radical scavenging capacity.

Effect of Intravascular Irradiation on Intimal Smooth Muscle Cells Proliferation and Apoptosis in Balloon Injuried Arteries

Objective: To investigate the effect of intravascular in radiation on thearterial wall smooth muscle cells (SMCs) proliferation and apoptosis after iliac artery bollominjury in figs. Methods: Twenty-seven miniature figs were divided into three groups. All pigsunderwent iliac artery balloon over-stretch. An^(192) Ir source through afterloader was positionedat the injuried segments to give 10 Gy in 9 pigs and 20 Gy in the other 9 pigs, and the rest 9 pigswere, used as control group. The pigs were killed on the 3rd, 10th and 28th days respectively forobservation. The injured segments were processed to examine SMCs proliferation by proliferation cellnuclear antigen (PCNA) and apopto-sis by terminal deoxynucleotidyl transferase-mediated dUTPnick-end labeling (TUNEL). Results: PC-NA index analysis has some that SMCs proliferation inneointima was significantly inhibited in irradiation group on the 10th and 28th days. The value forintimal SMCs apoptosis in control vs 10 Gy and 20 Gy irradiation groups were: (1. 185+-0. 49)% vs(2. 27+-0. 49)%(P>0. 05) and (1. 85+-0. 49)% vs (2. 53+-0. 45)%(P<0. 05), at the 10th day; (1.61+-0. 35)% vs (3. 11+-0. 51)%(P<0. 05), and (1.61+-0. 35)% vs (7. 05+-1. 82)% (P<0. 05), on the28th day. In irradiated arteries, the maximal incidence of intimal SMCs apoptosis was (7. 05+--1.82)% in 20 Gy group vs (3. 11+-0. 51)% in 10 Gy group (P<0. 05), on the 28th day. In the same doseirradiation group, the incidence of intimal SMCs apoptosis was higher on the 28th day than that onthe 10th day. Conclusion: Intra-arterial gamma irradiation can inhibit intimal SMCs proliferationand stimulate SMCs apoptosis in balloon-in jured arteries. These may be contributive to preventionof restenosis of arteries after balloon injury.

Urocortin, the neuropeptide, inhibits the viability of ECV304 cells and rat vascular smooth muscle cells

Objective: This study aims to investigate the effects of urocortin (Ucn) on the viability of endothelial cells (ECV304) and rat vascular muscle cells (VSMC). Methods: Rat aortic VSMC were isolated from the rats' thoracic aorta. We studied the effect of Ucn on the viability of ECV304 cells and VSMC by using a tetrazolium (MTT) assay.Results: Ucn (10 -7 mol/L) inhibited the viability of ECV304 cells and VSMC. Inhibition rates are 13% and 15%, respectively(P<0.05, compared with Control). This inhibition was not dependent on the affecting time and was not affected by the addition of ATP-sensitive potassium channel (KATP channel) blocker, glybenclamide (Gly, 10 mol/L). Conclusion: Ucn inhibits the viability of ECV304 and VSMC. Our results suggest that Ucn may be a new vasoactive agent and may have a beneficial effect in the process of vascular remodeling (VR).

Effects of Tetrandrine on Cytosolic Free Calcium in Cultured Bovine Aortic Smooth Muscle Cells

\ The effects of tetrandrine (Tet) on cytosolic free calcium ([Ca2+]i) in subcultured bovine aortic smooth muscle cells (SMC) were studied by Fura2 and ARCMMIC cation measurement system. Tet (1～100 μmol·L-1) had no effect on the resting [Ca2+]i, but had inhibitory effects on [Ca2+]i elevation induced by high K+, 5HT, ATP, Ang II and NE in the presence of extracellular Ca2+. High concentration of Tet also inhibited Pheinduced [Ca2+]i elevation in absence of extracellular Ca2+. Tet (1～100 μmol·L-1) inhibited KCl (60 mmol·L-1) induced [Ca2+]i elevation in dosedependent manner, the IC50 value was 9.2 (95% confidence limits: 5.7～14.9) mmol·L-1. The results suggested that Tet had blocking effects on both VOC and ROC in bovine aortic SMC. It appears that the mechanisms of blocking effect of Tet on ROC might be primarily due to its Ca2+ entry blocking effects.

Synergistic effect of a novel oxymatrine-baicalin combination against hepatitis B virus replication, a smooth muscle actin expression and typeⅠcollagen synthesis in vitro

AIM： To study the effect of oxymatrine-baicalin combination （OB） against HBV replication in 2.2.15 cells and α smooth muscle actin （ α SMA） expression, type I, collagen synthesis in HSC-T6 cells. METHODS： The 2.2.15 cells and HSC-T6 cells were cultured and treated respectively. HBsAg and HBeAg in the culture supernatants were detected by ELISA and HBV DNA levels were determined by fluorescence quantitative PCR. Total RNA was extracted from HSC-T6 cells and reverse transcribed into cDNA. The cDNAs were amplified by PCR and the quantities were expressed in proportion to β actin. The total cellular proteins extracted from HSC-T6 cells were separated by electrophoresis. Resolved proteins were electrophoretically transferred to nitrocellulose membrane. Protein bands were revealed and the quantities were corrected by β actin. RESULTS： In the 2.2.15 cell culture system, the inhibitory rate against secretion of HBsAg and HBeAg in the OB group was significantly stronger than that in the oxymatrine group （HBsAg, P = 0.043; HBeAg, P = 0.026; respectively）; HBV DNA level in the OB group was significantly lower than that in the oxymatrine group （P = 0.041）. In HSC-T6 cells the mRNA and protein expression levels of α SMA in the OB group were significantly lower as compared with those in the oxymatrine group （mRNA, P = 0.013; protein, P = 0.042; respectively）; The mRNA and protein expression levels of type I collagen in the OB group were significantly lower as compared with those in the oxymatrine group （mRNA, P 〈 0.01; protein, P 〈 0.01; respectively）.CONCLUSION： OB combination has a better effect against HBV replication in 2.2.15 cells and is more effective against α SMA expression and type I collagen synthesis in HSC-T6 cells than oxymatrine in vitro.

Baicalin inhibits PDGF-BB-stimulated vascular smooth muscle cell proliferation through suppressing PDGFRβ-ERK signaling and increase in p27 accumulation and prevents injury-induced neointimal hyperplasia

The increased proliferation and migration of vascular smooth muscle cells （VSMCs） are key events in the development of atherosclerotic lesions. Baicalin, an herb-derived flavonoid compound, has been previously shown to induce apoptosis and growth inhibition in cancer cells through multiple pathways. However, the potential role of baicalin in regulation of VSMC proliferation and prevention of cardiovascular diseases remains unexplored. In this study, we show that pretreatment with baicalin has a dose-dependent inhibitory effect on PDGF-BB-stimulated VSMC pro- liferation, accompanied with the reduction of proliferating cell nuclear antigen （PCNA） expression. We also show that baicalin-induced growth inhibition is associated with a decrease in cyclin E-CDK2 activation and increase in p27 level in PDGF-stimulated VSMCs, which appears to be at least partly mediated by blockade of PDGF recep- tor [~ （PDGFR~）-extracellular signal-regulated kinase 1/2 （ERK1/2） signaling. In addition, baicalin was also found to inhibit adhesion molecule expression and cell migration induced by PDGF-BB in VSMCs. Furthermore, using an animal carotid arterial balloon-injury model, we found that baicalin significantly inhibited neointimal hyperplasia. Taken together, our results reveal a novel function of baicalin in inducing growth arrest of PDGF-stimulated VSMCs and suppressing neointimal hyperplasia after balloon injury, and suggest that the underlying mechanism involves the inhibition of cyclin E-CDK2 activation and the increase in p27 accumulation via blockade of the PDGFR^-ERK1/2 signaling cascade.

Mechanisms simultaneously regulate smooth muscle proliferation and differentiation

Vascular smooth muscle cell （VSMC） differentiation and proliferation are two important physiological proc- esses during vascular development. The phenotypic alteration from differentiated to proliferative VSMC contrib- utes to the development of several major cardiovascular diseases including atherosclerosis, hypertension, resteno- sis after angioplasty or bypass, diabetic vascular complications, and transplantation arteriopathy. Since the VSMC phenotype in these pathological conditions resembles that of developing VSMC during embryonic development, understanding of the molecular mechanisms that control VSMC differentiation will provide fundamental insights into the pathological processes of these cardiovascular diseases. Although VSMC differentiation is usually ac- companied by an irreversible cell cycle exit, VSMC proliferation and differentiation occur concurrently during embryonic development. The molecular mechanisms simultaneously regulating these two processes, however, remain largely unknown. Our recent study demonstrates that cell division cycle 7, a key regulator of cell cycle, promotes both VSMC differentiation and proliferation through different mechanisms during the initial phase of VSMC differentiation. Conversely, Kriappel-like factor 4 appears to be a repressor for both VSMC differentia- tion and proliferation. This review attempts to highlight the novel role of cell division cycle 7 in TGF-β-induced VSMC differentiation and proliferation. The role of K141ppel-like factor 4 in suppressing these two processes will also be discussed.

Effect of tankyrase 1 on autophagy in the corpus cavernosum smooth muscle cells from ageing rats with erectile dysfunction and its potential mechanism

This study compared tankyrase 1 expression and autophagy quantity between erectile dysfunction （ED） and non-ED rats＇ corpus cavernosum smooth muscle cells （CSMCs）. This study aslo explored the effect and possible mechanism of tankyrase 1 on autophagy and cell proliferation in ageing ED rats＇ CSMCs. The intracavernous pres- sure and mean systemic arterial pressure were measured to investigate erectile function so that eight 24-month-old ED and eight 8-month-old male Wistar rats were choosed respectively. The rat CSMCs were isolated and cultured by enzyme digestion, in which tankyrase 1 expression and autophagy quantity were compared. Tankyrase 1 over-expression was induced with plasmid transfection by Lipofectamine^TM. The effect of tankyrase 1 overexpression on proliferation, autophagy and mTOR pathway in 24-month-old ED rats＇ CSMCs was measured by the cell growth curve in MTT assay, cell cycle analysis in flow cytometry （FCM）, key protein expression in Western blot, autophagy quantity in transmission electron microscopy, monodansylcadaverine staining and GFP-LC3 fluorescence. The primary CSMCs were confirmed by immunofluorescence, and the purity was 99.1% in FCM. Compared with that of 8-month-old rats, tankyrase 1 expression and autophagy quantity significantly decreased in 24-month-old ED rats＇ primary CSMCs （P 〈 0.01）. Tankyrase 1 overexpression significantly increased the growth rate （P 〈 0.05） and increased the S phase of cell cycle （P 〈 0.01）. The autophagosome quantity was remarkably increased （P 〈 0.01）, LC3-Ⅰ/Ⅱ and Beclin 1 were upregulated （P 〈 0.01 and P 〈 0.05）, and p-p70S6K （Thr389） was downregulated in 24-month-old ED rat CSMCs （P 〈 0.05）. In conclusion, Tankyrase 1 and autophagy decrease in the CSMCs from aging rats with ED, and tankyrase 1 may have a positive effect on proliferation by enhancing autophagy and regulating the mTOR signalling pathway.

Overexpression of heme oxygenase-1 protects smooth muscle cells against oxidative injury and inhibits cell proliferation

To investigate whether the expression of exogenous heme oxygenase-1 (HO-1) gene within vascular smooth muscle cells (VSMC) could protect the cells from free radical attack and inhibit cell proliferation, we established an in vitro transfection of human HO-1 gene into rat VSMC mediated by a retroviral vector. The results showed that the profound expression of HO-1 protein as well as HO activity was 1.8- and 2.0-fold increased respectively in the transfected cells compared to the non-transfected ones. The treatment of VSMC with different concentrations of H2O2 led to the remarkable cell damage as indicated by survival rate and LDH leakage. However, the resistance of the HO-1 transfected VSMC against H2O2 was significantly raised. This protective effect was dramatically diminished when the transfected VSMC were pretreated with ZnPP-IX, a specific inhibitor of HO, for 24 h. In addition, we found that the growth potential of the transfected cells was significantly inhibited directly by increased activity of HO-1, and this effect might be related to decreased phosphorylation of MAPK. These results suggest that the overexpression of introduced hHO-1 is potentially able to reduce the risk factors of atherosclerosis, partially due to its cellular protection against oxidative injury and to its inhibitory effect on cellular proliferation.

C-type natriuretic-peptide-potentiated relaxation response of gastric smooth muscle in streptozotocin-induced diabetic rats

AIM: To study the sensitivity of gastric smooth muscle to C-type natriuretic peptide (CNP) in streptozotocin (STZ)-induced diabetic rats. METHODS: The spontaneous contraction of a gastric smooth muscle strip was recorded by using physiological methods in rats. The expressions of CNP and natriuretic peptide receptor-B (NPR-B) in gastric tissue were examined by using immunohistochemistry techniques in the diabetic rat. RESULTS: At 4 wk after injection of STZ and vehicle, the frequency of spontaneous contraction of gastric smooth muscle was significantly reduced in diabetic rats, and the frequency was decreased from 3.10 ± 0.14 cycle/min in controls to 2.23 ± 0.13 cycle/min (n = 8, P < 0.01). However, the amplitude of spontaneous contraction was not significant different from the normal rat. CNP significantly inhibited spontaneous contraction of gastric smooth muscle in normal and diabetic rats, but the inhibitory effect was significantly potentiated in the diabetic rats. The amplitudes of spontaneous contraction were suppressed by 75.15% ± 0.71% and 58.92% ± 1.32% while the frequencies were decreased by 53.33% ± 2.03% and 26.95% ± 2.82% in diabetic and normal rats, respectively (n = 8, P < 0.01). The expression of CNP in gastric tissue was not changed in diabetic rats, however the expression of NPR-B was significantly increased in diabetic rats, and the staining indexes of NPR-B were 30.67 ± 1.59 and 17.63 ± 1.49 in diabetic and normal rat, respectively (n = 8, P < 0.01).CONCLUSION: The results suggest that CNP induced an inhibitory effect on spontaneous contraction of gastric smooth muscle, potentiated in diabetic rat via up-regulation of the natriuretic peptides-NPR-B-particulate guanylyl cyclase-cyclic GMP signal pathway.

Effect of rhubarb on contractile response of gallbladder smooth muscle strips isolated from guinea pigs

AIM: To investigate the effect of rhubarb on contractile response of isolated gallbladder muscle strips from guinea pigs and its mechanism.METHODS: Guinea pigs were killed to remove the whole gallbladder. Two or three smooth muscle strips (8 mm×3mm) were cut along the longitudinal direction. The mucosa on each strip was carefully removed. Each longitudinal muscle strip was suspended in a tissue chamber containing 5 mL Krebs solution (37 ℃), bubbled continuously with 950 mL/L O2 and 50 mL/L CO2. The resting tension (g), mean contractile amplitude (mm),and contractile frequency (waves/min) were simultaneously recorded on recorders. After 2-h equilibration, rhubarb (10, 20, 70, 200, 700, 1 000 g/L) was added cumulatively to the tissue chamber in turns every 2 min to observe their effects on gallbladder.Antagonists were given 3 min before administration of rhubarb to investigate the possible mechanism.RESULTS: Rhubarb increased the resting tension (from 0 to 0.40±0.02, P＜0.001), and decreased the mean contractile amplitude (from 5.22±0.71 to 2.73±0.41,P＜0.001). It also increased the contractile frequency of the gallbladder muscle strips in guinea pigs (from 4.09±0.46to 6.08±0.35, P＜0.001). The stimulation of rhubarb on the resting tension decreased from 3.98±0.22 to 1.58±0.12by atropine (P＜0.001), from3.98±0.22 to 2.09±0.19 by verapamil (P＜0.001) and from 3.98±0.22 to 2.67±0.43by phentolamine (P＜0.005). But the effect was not inhibited by hexamethonium (P＞0.05). In addition, the action of mean amplitude and frequency was not inhibited by the above antagonists.CONCLUSION: Rhubarb can stimulate the motility of isolated gallbladder muscle strips from guinea pigs. The stimulation of rhubarb might be relevant with M receptor,Ca2+ channel and α receptor partly.