Streptomycin inhibits electrophysiological changes induced by stretching of chronically infarcted rat hearts.

OBJECTIVE: To investigate stretch-induced electrophysiological changes in chronically infarcted hearts and the effect of streptomycin (SM) on these changes in vivo. METHODS: Sixty Wistar rats were divided randomly into four groups: a control group (n=15), an SM group (n=15), a myocardial infarction (MI) group (n=15), and an MI+SM group (n=15). Chronic MI was obtained by ligating the left anterior descending branch (LAD) of rat hearts for eight weeks. The in vivo blockade of stretch-activated ion channels (SACs) was achieved by intramuscular injection of SM (180 mg/(kg∙d)) for seven days after operation. The hearts were stretched for 5 s by occlusion of the aortic arch. Suction electrodes were placed on the anterior wall of left ventricle to record the monophasic action potential (MAP). The effect of stretching was examined by assessing the 90% monophasic action potential duration (MAPD90), premature ventricular beats (PVBs), and ventricular tachycardia (VT). RESULTS: The MAPD90 decreased during stretching in both the control (from (50.27±5.61) ms to (46.27±4.51) ms, P<0.05) and MI groups (from (65.47±6.38) ms to (57.47±5.76 ms), P<0.01). SM inhibited the decrease in MAPD90 during inflation ((46.27±4.51) ms vs. (49.53±3.52) ms, P<0.05 in normal hearts; (57.47±5.76) ms vs. (61.87±5.33) ms, P<0.05 in MI hearts). The occurrence of PVBs and VT in the MI group increased compared with that in the control group (PVB: 7.93±1.66 vs. 1.80±0.86, P<0.01; VT: 7 vs. 1, P<0.05). SM decreased the occurrence of PVBs in both normal and MI hearts (0.93±0.59 vs. 1.80±0.86 in normal hearts, P<0.05; 5.40±1.18 vs. 7.93±1.66 in MI hearts, P<0.01). CONCLUSIONS: Stretch-induced MAPD90 changes and arrhythmias were observed in chronically infarcted myocardium. The use of SM in vivo decreased the incidence of PVBs but not of VT. This suggests that SACs may be involved in mechanoelectric feedback (MEF), but that there might be other mechanisms involved in causing VT in chronic MI.

Regional differential expression of TREK-1 at left ventricle in myocardial infarction.

BACKGROUND: Altered membrane electrophysiology contributes to arrhythmias after myocardial infarction (MI). TREK-1 channel is essential in various physiological and pathological conditions through its regulation on resting membrane potential and voltage-dependent action potential duration. OBJECTIVES: The aim of this study was to investigate changes in gene expression and electrophysiology of TREK-1 in the left ventricle in a MI model. METHODS: Fifty-five rats were divided into 5 groups: sham-operated group, 6 hours, 24 hours, 3 days, and 7 days post MI group (n=11 per group). TREK-1 messenger RNA (mRNA) expression level in the infarct region (IR) and infarct border region (IBR) were quantified by real-time polymerase chain reaction (PCR), and TREK-1 current density at the IBR was recorded with whole-cell patch-clamp technique. RESULTS: TREK-1 mRNA expression decreased significantly in both endocardial and epicardial cells in the infarct region after MI. Conversely, TREK-1 increased significantly in endocardial and epicardial cells from the IBR (P<0.01). Current density of TREK-1 at IBR increased significantly in both epicardial and endocardial cells after MI (P<0.01). CONCLUSIONS: TREK-1 demonstrates specific changes in expression and electrophysiological function in left ventricle post MI. These results suggest that TREK-1 may participate in pathophysiologic alteration and electrical remodelling of left ventricular myocardium after MI, which may eventually lead to post-MI ventricular arrhythmias.

Early use of omeprazole benefits patients with acute myocardial infarction.

BACKGROUND: Bleeding complications are not uncommon in patients with acute myocardial infarction (AMI) during treatments. How to prevent the occurrence of upper gastrointestinal bleeding in AMI patients has become one of the most intractable problems. And there are conflicting data on the efficacy and complication rate of omeprazole treatment. We conducted an intervention study to determine whether using omeprazole could benefit AMI patients. METHODS: A total of 237 patients with AMI were divided into two groups at random: omeprazole group including 114 patients and control group including 123 patients. Omeprazole 40 mg by intravenous drip was given to the patients in omeprazole group when they were admitted to the hospitals. From the second day they were given omeprazole 20 mg per day by oral administration for 7 days. In contrast, no gastric acid inhibitor was given to the patients in control group. The incidence of upper gastrointestinal bleeding, the recanalization rate and overall mortality in both groups were observed. RESULTS: The incidence of upper gastrointestinal bleeding in omeprazole group was 5.3% (6/114) which was much lower than 14.6% (18/123) in control group (P = 0.017), but the recanalization rate had no significant difference between the two groups (P = 0.681). The overall mortality in omeprazole group was lower than that of control group (3.5% vs. 10.6%, P = 0.035). CONCLUSIONS: Our findings suggest that early use of omeprazole in AMI patients could decrease the incidence of upper gastrointestinal bleeding and the overall mortality, without influencing the recanalization rate. Early use of omeprazole might benefit AMI patients.

Relationship between testosterone and indexes indicating endothelial function in male coronary heart disease patients.

AIM: To investigate the relationship between androgen level and the indexes indicating endothelial function in male patients with coronary heart disease (CHD). METHODS: We registered the following data for 106 50-70-year-old men: age, weight, blood lipid, including total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol and triglyceride, whether a smoker, sugar levels, blood pressure, free testosterone (FT), vascular cell adhesion molecule-1 (VCAM-1) and the intima-media thickness (IMT) of common carotid artery, common carotid diameter, maximum velocity in systolic phase, minimum velocity in diastolic phase and resistant index. Among the 106 men, 51 were patients with CHD. The relationships between FT level, VCAM-1 concentration and IMT were examined, respectively, using a stepwise linear regression technique among all the 106 men. RESULTS: There was no statistical difference in terms of age, blood pressure, whether a smoker, sugar levels, HDL-C, minimum velocity in diastolic phase, resistant index between male CHD patients and controls; whereas results for weight, total cholesterol, low density lipoprotein cholesterol, triglyceride, VCAM-1 and IMT of male CHD patients were higher than those of controls; FT level and maximum velocity in systolic phase were lower. It was found that among all the objects, FT level was inversely correlated with IMT and VCAM-1 concentration. CONCLUSION: FT level was inversely correlated with VCAM-1 concentration and IMT which are indicators of endothelial function.

[The effect of homocysteine on fibrinolytic system in human umbilical vein endothelial cells].

OBJECTIVES: To investigate the relationship between homocysteine (Hcy) and the fibrinolytic system in acute myocardial infarction (AMI) and human umbilical vein endothelial cells (HUVEC). METHODS: Cultured HUVEC was divided into 10 groups (0, 10, 50, 200, 500 micromol/L Hcy with or without 15 micromol/L of folic acid). There were 53 patients of acute myocardial infarction (AMI) and 48 healthy controls. The plasminogen activator inhibitor-1 (PAI-1) and activator of plasminogen (tPA) antigen levels in HUVEC's supernatant and plasma were measured with Elisa kit. Concentration of plasma Hcy was measured by reverse-phase high-performance liquid chromatography with precolumn derivatization and fluorometric detection in the patients and healthy controls. Total RNA was extracted using the guanidinium isothiocyanate method. The semi-quantification of PAI-1 and tPA mRNA in HUVEC was carried out by reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: (1) PAI-1 mRNA and secreted protein levels were both significantly enhanced by Hcy at the concentration of 500 micromol/L, compared with the control group (P < 0.05). (2) The tPA mRNA and antigen levels were decreased significantly at concentration of 500 micromol/L of Hcy, compared with that of 10 micromol/L Hcy (P < 0.05), but compared with the control group (0 micromol/L), the tPA mRNA and antigen levels of 10 micromol/L of Hcy were much higher (P < 0.05). (3) The addition of folic acid reduced PAI-1 but increased tPA at both mRNA and protein levels, which were both obvious at concentrations of 500 micromol/L Hcy, compared with only Hcy group (P < 0.05). (4) Hcy, tPA, and PAI-1 antigen levels were increased in AMI group. Hcy is a independent risk factor of AMI (P < 0.05). There weren't significant correlation between Hcy and tPA or Hcy and PAI-1 in both groups (P > 0.05), although the coefficient correlation was higher in patients than in controls. CONCLUSIONS: These results suggested that hyperhomo-cysteinemia increased the incidence of thrombotic disease, which may be caused by decreasing the activity of fibrinolytic system, whereas, folic acid may be protective against the toxic action of Hcy.

[Testosterone has beneficial effects on human umbilical vein endothelial cells].

AIM: To investigate the influences of testosterone with varied concentrations on the functions of HUVEC. METHODS: Human umbilical vein endothelial cells within 2-3 passages were cultured with testosterone (3 x 10(-10) to 3 x 10(-8), 3 x 10(-6), 3 x 10(-5) mol/ L), and the control confluent cells were cultured in the same medium without steroid. MTT experiment was repeated for 7 days to investigate each groups' cell proliferation. The values of NO were tested as recommended. The tPA and PAI-1 antigen levels were assayed with ELISA Kits. RESULTS: Testosterone at physiologic or lower concentrations (3 x 10(-10) to 3 x 10(-8) mol/L ) had no adverse effect on A490 and NO level, meanwhile, stimulated the secretion of tPA (P < 0.01). However, tPA levels markedly reduced at larger dose (3 x 10(-6) to 3 x 10(-5) mol/L). On the other hand, PAI-1 antigen levels decreased significantly at the testosterone concentrations ranging from 3 x 10(-10) to 3 x 10(-5) mol/L (P < 0.05). CONCLUSION: Testosterone at physiologically relevant concentrations affectively decreased PAI-1, while increased tPA levels, which suggested that testosterone might have beneficial effects on the Human umbilical vein endothelial cells and cardiovascular system to prevent atherosclerosis.