Taurine attenuated β-glycerophosphate-stimulated calcification in cultured rat vascular smooth muscle cells

AIM: To investigate the effect of taurine on calcification of vascular smooth muscle cells (VSMCs).METHODS: Calcified VSMCs of rat in vitro were induced by β-glycerophosphate. Cellular calcium content, alkaline phosphatase(ALP) activities and [⁴⁵Ca]accumulation were measured. DNA synthesis were evaluated by [³H]-thymidine ( [³H]-TdR) incorporation. RESULTS: Calcium content, ALP activities and [⁴⁵Ca]uptake of calcified VSMCs stimulated by taurine (5-20 mmol/L) were greatly decreased in a concentration-dependent manner as compared with calcified group (P＜0.01). Taurine also inhibited the proliferation of calcified cells in a concentration-dependent manner. Cell countingz, [³H]-TdR incorporation of calcified cells stimulated by taurine were greatly decreased as compared with calcified VSMCs (P＜0.01). CONCLUSION: It was demonstrated that calcification of VSMCs may be alleviated by taurine.     

Effects of Liqustrazin on respiratory enzymes in the myocardial mitochondria of the ischemia-reperfusion rats

AIM: To study the effects of Liquestrazin on succinic dehydrogenase (SDH) and cytochrome oxidase (CCO) in the myocardial mitochondria of the ischemia-reperfusion rats and its mechanism. METHODS:Model of myocardial ischemia-reperfusion injury was produced by coronary artery ligation . The rats were devided into sham operation control (SC), ischemia-reperfusion (IR) and ischemia-reperfusion protected with Liqustrazin (IR+L) group . Activity of SDH,CCO,SOD and GSH·PX and contents of malondialdehyde (MDA),Cyt aa₃,Cyt c and phospholipid(PL) were observed respectively . RESULTS: As compared with ischemia-reperfusion group (IR), IR+L group showed significantly increased activity of SDH, CCO,SOD and GSH·PX (P＜0.01) , MDA content decreased significantly , the contents of Cyt aa₃ , Cyt c and PL increased respectively . CONCLUSION : Liqustrazin has notable antagonistic effects on decrease in SDH and CCO activities in the myocardial mitochondria of the ischemia-reperfusion rats , which is due to its oxygen free radicals scavenging action and its anti-lipid peroxidation reaction.     

Effect of homocysteine on secretion and expression of interleukin-6 in cultured rat vascular smooth muscle cells

AIM: To investigate the effect of homocysteine(Hcy) on secretion and expression of interleukin-6(IL-6), which is a multifunctional proinflammatory cytokine, in cultured rat vascular smooth muscle cells(VSMCs). METHODS: Rat VSMCs were stimulated with Hcy. Cell ELISA was performed to measure the expression of IL-6 protein and semiquantitative RT-PCR was used to dectect the IL-6 mRNA expression. RESULTS: Compared with control, treatment of 0.25 mmol Hcy for 6 h could increase IL-6 production. In addition, Hcy concentration-dependently increased the expression of IL-6 protein in these cells. 0.1 mmol/L, 0.25 mmol/L Hcy increased IL-6 production 1 4-fold and 3 4-fold, respectively Furthermore, RT-PCR analysis demonstrated that homocysteine also enhanced IL-6 mRNA expression in a concentration- and time-dependent manner.CONCLUSION: Homocysteine can induce IL-6 expression in VSMCs and elicit vascular inflammatory response, which may thereby influence the pathogenesis of atherosclerosis.     

Effects of taurine on the change of apoptosis induced by IL-1β, TNF-α and IFN-γ in rat pancreatic islet cells

AIM: To investigate the changes of apoptosis in isolated pancreatic islet cells, insulin secretion, expression of Bcl-xL and Bax induced by combination of IL-1β, TNF-α and IFN-γ, and effects of taurine on them.METHODS: Isolated pancreatic islet cells from Wistar rat were incubated in monolayer in vitro. NO^-₂/ NO^-₃ production, NOS activity, insulin secretion, the protein expression of Bcl-xL and Bax, percentage of islet cell apoptosis and DNA fragmentation in pancreatic islet cells incubated with combination of IL-1β, TNF-α and IFN-γ were measured, and the effects of taurine on the changes of them were further investigated. RESULTS: Combination of IL-1β, TNF-α and IFN-γ induced a significant increase in percentage of pancreatic islet cell apoptosis, NO^-₂/ NO^-₃ production and NOS activity, DNA ladder appearance, a decrease in insulin content, up-regulation in the protein expression of Bax and down-regulation in the protein expression of Bcl-xL (P<0.01), which were blocked by addition of taurine (P<0.01). These effects occurred in a dose dependent manner.CONCLUSION: Taurine attenuates β cell apoptosis induced by IL-1β, TNF-α and IFN-γ. The mechanism of which may be the inhibition of NOS activity and the decrease of NO production as well as the downregulation of Bax/Bcl-xL proportion.     

Effect of homocysteine on expression of interleukin-8 mRNA and protein in THP-1 macrophages

AIM: To investigate the effect of homocysteine (Hcy) on expression of interleukin-8 (IL-8) mRNA and protein in THP-1-derived macrophages (THP-1 macrophages). METHODS: Cultured THP-1 monocytes were induced to macrophages by 0.1 μmol/L PMA treatment for 72 hours, then the differentiated THP-1 macrophages were incubated with homocysteine (0.01 mmol/L-0.20 mmol/L) for 24 hours, or with 0.10 mmol/L Hcy for various time up to 48 hours. IL-8 protein in THP-1 supernatants was measured by ELISA, and IL-8 mRNA expression was detected by semiquantitive RT-PCR. RESULTS: Compared with control, Hcy significantly increased the expression of IL-8 protein in a concentration-dependent manner. 0.05 mmol/L, 0.10 mmol/L and 0.20 mmol/L Hcy increased IL-8 production by 1.28 fold, 1.32 fold and 1.55 fold, respectively (P＜0.01). IL-8 production were elevated significantly 3 h after treatment with 0.10 mmol/L Hcy. In addition, Hcy also increased IL-8 mRNA expression in a concentration-and time-dependent manner. CONCLUSION: Hcy may contribute to atherogenesis by inducing IL-8 expression and secretion in THP-1 macrophages.     

Injury of hepatic mitochondria and its pathogenesis in rats with endotoxemia

AIM:To investigate the effect of endotoxin on rat hepatic mitochondria.METHODS:Rats were randomly divided into two groups:endotoxin group and the control. 8 cases of animals were included in each group. The effect of electron leak on the production of endogenous oxygen free radicals and the changes of mitochondria function were studied.RESULTS:Treated with endotoxin, a significant increase in O₂ and the rate of state 3,4 were observed in liver mitochondria; The rate of electron transfer to proton pump of mitochondria respiratory chain complex Ⅱ+Ⅲ(H⁺/2e^-), respiratory control rate and ADP/O decreased significantly.CONCLUSION:A increase in production of endogenous oxygen free radicals induced by endotoxin plays an important role in the injury of rat liver mitochondria.     

The effect of homocysteine on airway smooth muscle cells and fibroblasts

AIM: To study the effect of homocysteine (HCY) on proliferation of airway smooth muscle cells and fibroblasts and the effect of HCY on collagen prodution of airway fibroblasts. METHODS: [³H]-TdR incorpora- tion was measured in cultured airway smooth muscle cells. The [³H]-TdR and [³H]-proline incorporation were mea- sured in cultured airway fibroblasts. RESULTS: HCY induced proliferation of airway smooth muscle cells and fibroblasts in a concentration - dependent manner. HCY also induced collagen production of airway fibroblasts in a concentration - dependent manner. The inhibitors of protein kinase C, H7 and polymyxin B, inhibited HCY - induced proliferation of airway smooth muscle cells. CONCLUSIONS: HCY induced proliferation of airway smooth muscle cells and fibroblasts, HCY also induced collagen production of airway fibroblasts. The HCY - induced proliferation of airway smooth muscle cells may be related to the pathway of PKC signal transduction.     

Effect of peroxisome proliferator activated receptor δ on mRNA expression of MCP-1 induced by homocysteine in cultured human umbilical vein endothelial cells

AIM: To investigate the effects of peroxisome proliferator activated receptor δ (PPARδ) on the mRNA expression of monocyte chemoattractant protein 1 (MCP-1) induced by homocysteine (Hcy) in human umbilical vein endothelial cells (HUVECs). METHODS: Collagenase was used to isolate endothelial cells from human umbilical vein, and the cells were cultured in vitro . The HUVECs were divided into blank control group, Hcy group, GW0742 (a specific agonist of PPARδ) group and diphenyleneiodonium (DPI,a specific inhibitor of NADPH oxidase) group. RT-PCR was used to examine the mRNA expression of MCP-1 and PPARδ. The protein level of PPARδ was detected by Western blotting.2',7'-Dichlorofluorescin diacetate(DCFH-DA) was added to monitor intracellular production of reactive oxygen species (ROS). RESULTS: Compared with control group, Hcy promoted the mRNA expression of MCP-1 in a concentration-dependent manner, and decreased the mRNA expression of PPARδ in HUVECs. The mRNA expression of MCP-1 was significantly elevated by Hcy at the concentration of 10^-5 mol/L, and the mRNA expression of PPARδ was decreased remarkably (P<0.01). GW0742 decreased the mRNA expression of MCP-1 compared with Hcy group (P<0.01). Hcy remarkably increased the production of ROS compared with control group. Hcy-induced production of ROS was also significantly attenuated by GW0742. CONCLUSION: The activation of PPARδ decreases the Hcy-induced mRNA expression of MCP-1 by suppressing Hcy-stimulated production of ROS.     

Metallothionein inhibits rat vascular fibroblasts activation induced by homocysteine

AIM:To study the effects of exogenous metallothionein (MT) and ZnCl₂-induced MT production on biological action of homocysteine(HCY)in vascular fibroblasts.METHODS:[³H]-TdR, [³H]-Pro incorporation and LDH leakage were measured, the cellular viabilities were calculated by trypan blue exclusion test and the intracellular contents of MT were assayed by [¹⁰⁹Cd]-hemoglobin saturation method in cultured rat vascular fibroblasts.RESULTS:Proliferation, collagen production of vascular fibroblasts in HCY-treated group were significantly increased compared with control group in a concentration-depedant manner. HCY (500 μmol/L) increased LDH leakage and decreased the cellular viabilities (P＜0.05 or P＜0.01). [³H]-TdR incorporation, [³H]-Pro incorporation, collagen secretion and LDH leakage were all decreased in MT (1×10^-5 mol/L, 1×10^-4mol/L) plus HCY(500 μmol/L) incubated group, compared with HCY alone group, respectively (P＜0.05 or P＜0.01). MT content in ZnCl₂ pretreatment group was increased compared with control group. Proliferation, collagen production and LDH leakage in HCY group pretreated with ZnCl₂ were decreased whereas the cellular viabilities were increased compared with HCY alone group.CONCLUSIONS:The results shows that HCY induces proliferation and collagen production of vascular fibroblasts. Both exogenous MT and endogenous MT induced by ZnCl₂ inhibite the above-mentioned effects of HCY on vascular fibroblasts. MT inhibites vascular fibroblast activation induced by HCY, which may be related to its vascular protection.     

Effect of taurine on kidney injury induced by paraquat poisoning in rats

AIM:To study the effects of taurine at different doses on renal oxidative stress and inflammation induced by paraquat in rats.METHODS:Male SD rats (n=48) were randomly divided into 4 groups:negative control group,paraquat group,paraquat+low-dose taurine group,and paraquat+high-dose taurine group.The serum levels of creatinine and urea nitrogen were detected by a biochemical analyzer.The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were measured by colorimetry.The plasma concentrations of IL-6 and intercellular adhesion molecule (ICAM)-1 were detected by ELISA.Renal reactive oxygen species (ROS) was checked by fluorescence probe dihydroethidium (DHE).The protein levels of renal p-P38 MAPK,p-ERK1/2 and p-JNK were determined by Western blot.The mRNA expression of TNF-α,IL-6 and TGF-β1 was detected by real-time PCR.RESULTS:Serum creatinine and urea nitrogen increased after paraquat poisoning,and decreased after feeding with taurine in poisoned rats,with better result in high-dose taurine group.Taurine reduced the oxidative stress and inflammation in the renal tissue,and also reduced the protein levels of p-JNK,p-ERK1/2 and p-P38 in the kidney of paraquat-poisoned rats.CONCLUSION:Taurine attenuates renal injury induced by paraquat poisoning in rats.The mechanism may be related to reducing renal MAPK activity,oxidative stress and inflammatory response.     

Effects of Shenmai injection on acute myocardial ischemia/reperfusion injury in rats

AIM: To observe the effect of Shenmai injection on the acute myocardial ischemia/ reperfusion injury in rats. METHODS: The left-anterior coronary artery was ligated for 10 minutes and then loosed for 15 minutes to establish the animal model of acute myocardial ischemia/reperfusion injury. During the process, electrocardiogram was traced continuously to observe the arrhythmia caused by reperfusion. The levels of SOD, MDA, Na⁺, K⁺-ATPase and Ca²⁺ -ATPase in ventricular myocardium were measured. The mitochondria was observed through electron microscope. RESULTS: Shenmai injection decreased the incidence of arrhythmia caused by reperfusion and shortened its duration. Shenmai injection improved the activity of SOD, Na⁺, K⁺-ATPase and Ca²⁺ -ATPase, decreased the content of MDA in myocardium and relieved the injury of mitochondria. CONCLUSION: Shenmai injection had a protective effect on acute myocardial ischemia/reperfusion injury in rats. The mechanism may be related to relieving the injury caused by oxygen free radical and calcium overload.     

Metallothionein inhibits homocysteine-induced proliferation of rat vascular smooth muscle cells

AIM:To investigate the effect of metallothionein(MT) on proliferation of rat vascular smooth muscle cells (VSMCs) stimulated by homocysteine and its mechanism. METHODS:VSMCs proliferation was measured by [³-H]-TdR incorporation, mitogen-activated protein kinase(MAPK)activity were determined by immunoprecipitation method, the intracellular contents of MT and malondialdehyde (MDA)were assayed by -hemoglobin saturation method and TBA reaction, respectively, and lactate dehydrogenase (LDH) leakage was measured by NADH oxidation. RESULTS:Hcy(10^-6-10^-4 mmol/L) stimulated [³-H]-TdR incorporation by the VSMCs in a concentration-dependent manner. Compared with control, [³-H]-TdR incorporation in VSMCs treated with 0.1 mmol/L Hcy was increased by 4.2 fold (P＜0.01). Meanwhile, Hcy enhanced MAPK activity, MDA formation and LDH release (P＜0.01)in a concentration-dependent manner. Treatment of VSMCs with MT alone did not change above parameters, compared with control. However, MT (10^-6-10^-4 mol/L)attenuated significantly Hcy-stimulated proliferation of VSMCs (P＜0.01)in a concentration-dependent manner. And MT inhibited obviously Hcy-induced activation of MAPK activity, MDA formation and LDH release. Preincubation of VSMCs with 0.5 mmol/L ZnCl₂ for 6 h induced an increase cellular MT content by 5.7-fold (P＜0.01). The MT-overexpressed VSMCs resisted Hcy-stimulating action on MAPK activity, MDA formation and LDH leakage (P＜0.01). CONCLUSION:These results show that MT has an inhibitory effect on Hcy-induced VSMCs proliferation, and that MT could inhibit Hcy-stimulated MAPK activity and lipid peroxidation.     

Effect of taurine on action potentials and ATP-sensitive posstiaum channel activity during hypoxia in ventricular muscle of guinea pig

AIM: To study the effects of taurine on ATP sensitive potassium channel (IK-ATP) during hypoxia in single ventricular myocyte. METHODS: The model of myocardial hypoxia was induced by unmixed and saturated nitrogen. IK-ATP activities were measured by whole-cell patch clamp recording. RESULTS: Activities of IK-ATP in the cell membrane of hypoxia ventricular myocyte significantly increased, compared to that in the normal. Extracellular injection of taurine (5，10，20 mmol/L) inhibited the increase in the IK-ATP activity in the hypoxia myocardium in a concentration-depend manner. Injection of taurine also recovered shorten APD during hypoxia. CONCLUSIONS: Taurine produces its cardioprotective effect by inhibiting the activity of IK-ATP in the hypoxia cardiomycytes of guinea pig. The results suggest that the depletion of taurine during myocardial hypoxia contributes to the early activation of the KATP channel.     

Effect of L-arginine on function and structure of mitochondria in ischemia-reperfusion myocardial cells in rabbits

AIM: To study the effect of L-arginine (L-Arg) on function and structure of mitochondria in ischemia-reperfusion (MRI) myocardial cells. METHODS: Thirty rabbits were randomly divided into three groups (n=10 in each), control group, MIR group and MIR+L-Arg group. The mitochondrial respiratory function, Ca²⁺ concentration ([Ca²⁺]m), malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were determined. Meanwhile, the contents of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), total adenylic acid number (TAN) and energy charge (EC) in the myocardial tissue were respectively measured. Moreover, the ultrastructure changes in myocardial mitochondria were observed during MIR. RESULTS: The mitochondrial respiratory control rate (RCR), velocity 3 (V₃), SOD, surface density (Sv) and specific surface (δ) in MIR+L-Arg group were higher than those in MIR group, velocity 4 (V₄), [Ca²⁺]m, MDA, volume density (Vv), horizental diameter (Hd) were lower than those in MIR group. ATP, ADP, TAN and EC levels of myocardial tissue were higher than those in MIR group. There was no significant difference between MIR+L-Arg and control group in V₃, V₄, SOD, MDA, Vv, Sv, δ, Nv, Vd, AMP and TNA. CONCLUSION: It is suggested that L-Arg improves the function and structure of mitochondria in myocardial cells in the reperfusion injury after myocardial ischemia by decreasing oxygen free radical level and Ca²⁺ overload in the mitochondria.     

Effects of taurine on expression of glucose transporters in rat brain with diffused brain injury

AIM: To investigate the effect of taurine on the expression of glucose transporter 1 (GLUT1) and transporter 3 (GLUT3) in rat brain with diffused brain injury (DBI).METHODS: Sixty-four male Sprague-Dawley rats were randomly divided into 4 groups: sham-operated group, DBI group, low-dose taurine group (200 mg/kg, ig) and high-dose taurine group (300 mg/kg, ig).After fed with the corresponding drugs for 7 days, the animal model of DBI was made, and the rats were executed 24 h after DBI.The expression of GLUT1 and GLUT3 in the brain was detected by the methods of immunohistochemistry and Western blotting.The pathomorphological changes of the cerebral cortex were observed under electron microscope.RESULTS: The expression of GLUT1 was detected in capillary vascular endothelial cells in each group, and cytoplasm-positive cells or the cells with buffy membrane were observed.No significant difference of the GLUT1 expression in brain tissues between DBI group and sham-operated group was detected.Compared with DBI group, the expression of GLUT1 in the brain tissues were significantly increased in low-and high-dose taurine groups (P<0.01).The expression of GLUT1 in the brain tissues in low-dose taurine group were significantly higher than that in high-dose taurine group (P<0.05).The positive staining of GLUT3 only appeared in the periphery of the third ventricle in each group in the cells with buffy membrane or positive cytoplasm.The expression of GLUT3 in the brain tissues in DBI group was significantly higher than that in sham-operated group (P<0.01).The expression of GLUT3 in the brain tissues in low-and high-dose taurine groups was significantly higher than that in DBI group (P<0.01).Compared with low dose taurine group, the expression of GLUT3 in the brain tissues were significantly increased in high-dose taurine group (P<0.01).The pathological damage of cerebral cortex in low-dose taurine group was obviously alleviated.CONCLUSION: Taurine may take part in the neuroprotective mechanisms in DBI by increasing the expression of GLUT1 and GLUT3 at protein level to maintain the energy supply in brain tissues.     

Effect of homocysteine on the apoptosis of cultured human umbilical vein endothelial cells

AIM: To investigate the effect of homocysteine(Hcy) on the apoptosis of endothelial cells (EC). METHODS: First-passaged human umbilical vein endothelial cells (hUVEC) were cultured with M199 containing 3 mmol/L Hcy. hUVEC apoptosis was detected as follow: demonstration of nuclear changes by Hoechst 33258 staining, agarose gel electrophoresis of DNA fragments, detection of apoptotic cells by flow cytometry following Annexin V-PI doubled stain, Western blot for P53 and Bax protein detection and colorimetry detecting caspase-3 activity. RESULTS: Compared with control, homocysteine induced characteristic apoptotic changes in hUVEC. The chromosomal DNA of hUVEC appeared "DNA ladder" by agarose gel electrophoresis. Apoptotic cells were increased significantly (P<0.01, n=3). Hcy promoted the expression of protein Bax, P53 (P<0.01, n=3) and enhanced the activity of caspase 3 (P<0.05, n=3). CONCLUSION: Homocysteine induces apoptosis in cultured hUVEC.     

Inhibition of endothelin on taurine-transportation in rat cardiac myocytes

AIM:To investigate the effect of endothelin(ET) on taurine transportation in rat cardiac myocytes in vitro.METHODS: In cultured cardiac myocytes of neonatal rats, taurine transportation velocity was measured by radio-ligand method. RESULTS: ET(10^-10-10^-8 mol/L) could inhibit taurine transportation in a dose-dependent manner.10^-10,10^-9 and 10^-8mol/L of ET significantly decreased taurine transpotation by 13%, 38% and 71%, respectively (P＜0.01), compared with control group. H₇,BQ123 and Pre-PMA can reverse the inhibition of ET on taurine transportation dramatically(P＜0.01).CONCLUSION:The binding of ET and ET-A receptor might activate protein kinase C,which inhibits taurine transportation in cultured myocytes of rats.     

Plasma homocysteine levels in health adult subjects with different age and sex

AIM: To establish a guidance of homocysteine (Hcy) level in healthy adults for prevention and treatment of high plasma Hcy by determining the Hcy concentration in healthy subjects with different sex and age.METHODS: After the common factors of the high plasma Hcy such as hypertension, stroke, coronary heart disease and so on were eliminated, 738 subjects were selected and divided into 3 groups: the young (≤35), the middle-aged (≥36, <60) and the old age (≥60). According to the ages, the male and female subgroups were also divided. The plasma Hcy levels were determined by enzymatic cycling assay.RESULTS: The Hcy levels in the males were higher than those in the females in each group (P<0.01) and the levels of Hcy increased with age in both groups. The concentrations of Hcy between the groups of young, the middle-aged and the old age were obviously different (P<0.01). The mean value in male was 13.26 μmol/L vs that in female of 9.68 μmol/L (P<0.01). In most males (73.21%), the Hcy levels were 10.01-15.00 μmol/L. The Hcy levels in most females (84.06%) were < 10.00 μmol/L. CONCLUSION: The plasma Hcy levels are obviously different in healthy adults according to the sex and age: the Hcy levels in the males are higher than those in the females, and increases gradually with age. To determine the maximum level of plasma Hcy in healthy adults, the factors of sex and age should be considered.     

Involvement of mtNOS in the Ca2+-induced damages of myocardial mitochondria during the early stage after severe burns

AIM:To study the role of mitochondrial nitric oxide synthase (mtNOS) in the damages of myocardial mitochondria during the early stage after severe burns.METHODS:An experimental model of 30% TBSA full-thickness skin scalding was reproduced in rats. Myocardial mitochondria were isolated from control and burned rats at 1, 3, 6, 12 and 24 h postburn. The mitochondrial respiratory function, content of mitochondrial calcium( [Ca²⁺]_m) and activities of mtNOS and cytochrome c oxidase were determined. RESULTS: (1) Myocardial mitochondrial respiratory control rate(RCR) at 1 h was evidently higher than that of control, but at 3, 6, 12 and 24 h postburn, it was significantly lower than that of the control. The changes in ST₃ is parallel to those of RCR, and ST₄ was evidently increased only at 3 h postburn. (2) [Ca²⁺]_m was higher at all time points postburn and the activity of mtNOS was higher significantly only at 3, 6, 12 and 24 h than that of the control. The activity of cytochrome c oxidase at the 3, 6, 12 and 24 h was low comparing to the control. (3) After severe burns, RCR was negatively correlated with mtNOS activity(r=0.9347, P＜0.05) and mtNOS activity was positive correlated with [Ca²⁺]_m (r=0.8945, P＜0.05). CONCLUSION:The elevation of [Ca²⁺]_m significantly activates mtNOS, which might play an important role in the damages of myocardial mitochondria during the early stage after burn injury.     

Effects of Ang Ⅱ on the production of ET-1, NO from adult rat myocardial fibroblasts

AIM: To investigate the effects of Ang Ⅱon the production of ET-1, NO from myocardial fibroblasts (MFs) of adult rat. METHODS: MFs were extracted by enzymatic digestion and anchorage velocity-dependent separation method. In this study, the changes of ET-1 and NO production from MFs in the second passage were examined by radioimmunoassay and by nitrate reductase-dependent assay, separatively. RESULTS: In a specific concentration range, AngⅡ increased ET-1 synthesis in MFs in a concentration-dependent manner. Losartan, the antagonist of angiotensin Ⅱ 1 type recepters (AT₁R), blocked the above effects. Ang Ⅱ may inhibit NO synthesis in MFs. When MFs were treated with losartan+Ang Ⅱ, the production of NO increased significantly, and was higher than that treated with the others (P<0.01). CONCLUSION: Ang Ⅱ may increase the production of ET-1 in MFs via AT₁R and affect NO production in MFs mainly via AT₁R to change the ratio of ET-1 and NO. Ang Ⅱ maybe exert inductive effects on myocardial hypertrophy and heart failure by affecting these complicated balances between bioactive factors produced from MFs.