In order to investigate the effects of aconitine on [Ca2+] oscillation patterns in cultured myocytes of neonatal rats, fluorescent Ca2+ indicator Fluo-4 NW and laser scanning confocal microscope (LSCM) were used to detect the real-time changes of [Ca2+] oscillation patterns in the cultured myocytes before and after aconitine (1.0 micromol/L) incubation or antiarrhythmic peptide (AAP) and aconitine co-incubation. The results showed under control conditions, [Ca2+] oscillations were irregular but relatively stable, occasionally accompanied by small calcium sparks. After incubation of the cultures with aconitine, high frequency [Ca2+] oscillations emerged in both nuclear and cytoplasmic regions, whereas typical calcium sparks disappeared and the average [Ca2+] in the cytoplasm of the cardiomyocyte did not change significantly. In AAP-treated cultures, intracellular [Ca2+] oscillation also changed, with periodic frequency, increased amplitudes and prolonged duration of calcium sparks. These patterns were not altered significantly by subsequent aconitine incubation. The basal value of [Ca2+] in nuclear region was higher than that in the cytoplasmic region. In the presence or absence of drugs, the [Ca2+] oscillated synchronously in both the nuclear and cytoplasmic regions of the same cardiomyocyte. It was concluded that although oscillating strenuously at high frequency, the average [Ca2+] in the cytoplasm of cardiomyocyte did not change significantly after aconitine incubation, compared to the controls. The observations indicate that aconitine induces the changes in [Ca2+] oscillation frequency other than the Ca2+ overload.
Aconitine/*pharmacology ; Animals, Newborn ; Calcium Signaling/*drug effects ; Cells, Cultured ; Myocytes, Cardiac/cytology ; Myocytes, Cardiac/*metabolism ; Rats, Sprague-Dawley

Action Potentials ; drug effects ; Animals ; Cadmium ; toxicity ; Guinea Pigs ; Male ; Myocytes, Cardiac ; drug effects ; physiology

AIMTo study the effect of thyroid hormone on protein kinase C activity and isoprotein expressions in cardiac myocytes and fibroblasts of rats in vitro.

METHODSCardiac myocytes and fibroblasts were cultured according to the method of Simpson. Cells were pretreated with 1% newborn calf serum (NCS) or Angiotensin II (Ang II) for 24 hours, then Triiodothyronine (T3) was added to the culture medium and the culture was kept for another 48 hours. The protein kinase C activation were measured by PepTaga non-radioactive PKC assay, and the expressions of PKC alpha and PKC epsilon were detected by Western blot method.

RESULTSAt the condition of 1% NCS culture medium, T3 could inhibit PKC activity and PKC epsilon expression in cardiac myocytes significantly, but the expression of PKC alpha in cardiac myocytes was not influenced by T3. In cardiac fibroblasts, neither PKC activity nor PKC alpha and PKC epsilon expressions was influenced by T3. When cells were pretreated with Ang II for 24 hours, PKC activities in cardiac myocytes and fibroblasts were increased significantly, and PKC epsilon expressions in cardiac myocytes were also markedly increased. Following a T3 treatment, PKC activity and PKC epsilon expression in cardiac myocytes were markedly decreased, but PKC activity in cardiac fibroblasts was not changed.

CONCLUSIONWhether at the condition of 1% NCS medium or in a pretreatment with Ang II, thyroid hormone could inhibit the PKC activity and PKC epsilon expression in cardiac myocytes. The influence of thyroid hormone on the PKC signal pathway in cardiac myocyte may be involved in many pathophysiological progress of myocardium.

Animals ; Cells, Cultured ; Myoblasts, Cardiac ; drug effects ; metabolism ; Myocytes, Cardiac ; drug effects ; metabolism ; Protein Kinase C ; metabolism ; Rats ; Rats, Wistar ; Signal Transduction ; drug effects ; Thyroid Hormones ; pharmacology

AIMTo learn the electrophysiological interference of levofloxacin (LVFX) to heart in guinea pig.

METHODSHigh, moderate and low doses of LVFX were given to the anesthetic guinea pig via i.p., and QT interval span and corrected QT-interval span in the II leading lines of ECG were recorded and analyzed from 5 min to 360 min after the drug administration. Single ventricular myocytes were obtained and impacted by LVFX solution of different concentrations. Then delayed rectifier potassium currents (I(K)) on single cells were recorded with whole-cell patch clamp technique, and compared with control group(without impact of LVFX).

RESULTS(1) After the administration of LVFX, at the dose of 200 mg/kg. QT-interval span was significantly elongated, and the increasing rate is 19.38% +/- 3.15% (P < 0.05). While at the relatively lower doses of 50 mg/kg and 100 mg/kg, the elongation is of low/no significance (P > 0.05). (2) LVFX inhibited I(K) dose-dependently and time-dependently.

CONCLUSIONLVFX might prolong the QT-interval span by the mechanism of inhibiting I(K), which implies a potential risk in clinical application.

Animals ; Guinea Pigs ; Levofloxacin ; Membrane Potentials ; Myocytes, Cardiac ; drug effects ; physiology ; Ofloxacin ; pharmacology ; Patch-Clamp Techniques

Animals ; Apoptosis ; drug effects ; Ginsenosides ; pharmacology ; Myocardial Reperfusion Injury ; pathology ; Myocytes, Cardiac ; cytology ; Rats ; Rats, Wistar

To investigate the electrophysiological effects of 17β-estradiol on pacemaker cells in sinoatrial (SA) nodes of rabbits and the underlying mechanism, intracellular microelectrode technique was used to record action potential (AP) in SA node cells of rabbits. The results showed that: (1) 17β-estradiol (1, 10, 100 μmol/L) not only significantly decreased the amplitude of action potential (APA) and the maximal rate of depolarization (V(max)), but also decreased the velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF) in a concentration-dependent manner. The AP duration at 50% repolarization (APD(50)) and at 90% repolarization (APD(90)) were prolonged. But the maximal diastolic potential (MDP) was not affected. (2) Pretreatment with tamoxifen (10 μmol/L), an inhibitor of estrogen receptor, did not block the electrophysiological effects of 17β-estradiol (10 μmol/L) on SA node cells. (3) Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 μmol/L), a nitric oxide (NO) synthase inhibitor, completely abolished the electrophysiological effects of 17β-estradiol (10 μmol/L) on SA node cells. The results suggest that 17β-estradiol inhibits the electrophysiological activity of pacemaker cells in SA nodes of rabbits in a concentration-dependent manner possibly through a non-genomic mechanism related with NO.
Action Potentials ; Animals ; Electrophysiological Phenomena ; Estradiol ; pharmacology ; Myocytes, Cardiac ; drug effects ; Rabbits ; Sinoatrial Node ; cytology

AIMTo study the effect of Dehydrocorydaline and Verapamil (Ver) on intracellular free calcium concentration of myocardial cell ([Ca2+]i) under hypoxic condition.

METHODSWe adopted guinea-pig heart Langendorff instillation. The myocardial cells were isolated by collagenase (Type I, sigma)and marked by fluorescence ratio imaging. The suspension of myocardial cells was assigned to six groups: DHC, Ver, and control were each two. Each three groups was exposed to hypoxia and normoxia before determination of [Ca2+]i.

RESULTS(1) In normoxia state, [Ca2+]i was 120.5-8.3 nml/L (n = 20).( 2) In hypoxia state, the increased [Ca2+]i of myocardial cells was proportional to the time (degree) of hypoxia. Correlation coefficient (r) was about 0.98. (3) Under the condition of normoxia DHC and Ver decreased [Ca2+]i. (4) DHC was obviously slow the increase of [Ca2+]i after hypoxia.

CONCLUSIONIn normoxia and hypoxia, DHC decreases the increased [Ca2+]i. It can prevent intracellular calcium overload. We believe DHC may improve self-protected performance of myocardial cells.

Alkaloids ; pharmacology ; Animals ; Calcium ; metabolism ; Cell Hypoxia ; Female ; Guinea Pigs ; Male ; Myocytes, Cardiac ; drug effects ; metabolism

This study is aimed to investigate the intervention effect and possible mechanism of ophiopogonin D( OPD) in protecting cardiomyocytes against ophiopogonin D'( OPD')-induced injury,and provide reference for further research on toxicity difference of saponins from ophiopogonins. CCK-8 assay was used to evaluate the effect of OPD and OPD' on cell viability. The effect of OPD on OPD'-induced cell apoptosis was measured by flow cytometry. Morphologies of endoplasmic reticulum were observed by endoplasmic reticulum fluorescent probe. PERK,ATF-4,Bip and CHOP mRNA levels were detected by Real-time quantitative polymerase chain reaction( PCR) analysis. ATF-4,phosphorylated PERK and e IF2α protein levels were detected by Western blot assay. RESULTS:: showed that treatment with OPD'( 6 μmol·L-1) significantly increased the rate of apoptosis; expressions of endoplasmic reticulum stress related genes were increased. The morphology of the endoplasmic reticulum was changed. In addition,different concentrations of OPD could partially reverse the myocardial cell injury caused by OPD'. The experimental results showed that OPD'-induced myocardial toxicity may be associated with the endoplasmic reticulum stress,and OPD may modulate the expression of CYP2 J3 to relieve the endoplasmic reticulum stress caused by OPD'.
Apoptosis ; Cardiotonic Agents ; pharmacology ; Cells, Cultured ; Endoplasmic Reticulum Stress ; drug effects ; Humans ; Myocytes, Cardiac ; drug effects ; Saponins ; pharmacology ; Spirostans ; pharmacology

Rhizoma Polygoni Cuspidati, a Chinese herbal drug, has actions of dispelling dampness, alleviating jaundice, clearing heat, subsiding toxin, activating blood, and removing stasis. Polydatin (PD), one of its chief active ingredients, has been proved by modern pharmacological studies to possess extensive cardiovascular pharmacological activity, showing marked effects on protecting cardio-myocyte, dilating blood vessel, antagonizing platelet aggregation, thrombosis, and atherosclerosis. The progress of the research on cardiovascular pharmacological actions and the acting mechanism of PD was reviewed in this paper.
Biomedical Research ; trends ; Cardiovascular System ; drug effects ; Glucosides ; pharmacology ; Humans ; Lipid Peroxidation ; drug effects ; Myocytes, Cardiac ; drug effects ; Stilbenes ; pharmacology ; Vasodilation ; drug effects

OBJECTIVE: To investigate the protective effect of melatonin against myocardial ischemia reperfusion (IR) injury in isolated rat hearts and explore the underlying mechanisms. METHODS: The isolated hearts from 40 male SD rats were randomly divided into 4 groups (=10): the control group, where the hearts were perfused with KH solution for 175 min; IR group, where the hearts were subjected to global ischemia for 45 min followed by reperfusion for 120 min; IR+melatonin (Mel+IR) group, where melatonin (5 μmol/L) was administered to the hearts 1 min before ischemia and during the first 5 min of reperfusion, followed by 115 min of reperfusion; and IR+2, 3-butanedione monoxime (IR+BDM) group, where the hearts were treated with BDM (20 mmol/L) in the same manner as melatonin treatment. Myocardial injury in the isolated hearts was assessed based on myocardial injury area, caspase-3 activity, and expressions of cytochrome C and cleaved caspase-3 proteins. Cardiac contracture was assessed using HE staining and by detecting lactate dehydrogenase (LDH) activity and the content of cardiac troponin I (cTnI) in the coronary outflow, measurement of left ventricular end-diastolic pressure (LVEDP) and electron microscopy. The content of ATP in the cardiac tissue was also determined. RESULTS: Compared with those in the control group, the isolated hearts in IR group showed significantly larger myocardial injury area and higher caspase-3 activity and the protein expressions of cytochrome C and cleaved caspase-3 with significantly increased LDH activity and cTnI content in the coronary outflow and elevated LVEDP at the end of reperfusion; HE staining showed obvious fractures of the myocardial fibers and the content of ATP was significantly decreased in the cardiac tissue; electron microscopy revealed the development of contraction bands. In the isolated hearts with IR, treatment with Mel or BDM significantly reduced the myocardial injury area, caspase-3 activity, and protein expressions of cytochrome C and cleaved caspase-3, obviously inhibited LDH activity, lowered the content of cTnI and LVEDP, reduced myocardial fiber fracture, and increased ATP content in the cardiac tissue. Both Mel and BDM inhibited the formation of contraction bands in the isolated hearts with IR injury. CONCLUSIONS Mel can alleviate myocardial IR injury in isolated rat hearts by inhibiting cardiac contracture, the mechanism of which may involve the upregulation of ATP in the cardiac myocytes to lessen the tear of membrane and reduce cell content leakage.
Animals ; Heart ; drug effects ; Male ; Melatonin ; pharmacology ; therapeutic use ; Muscle Contraction ; drug effects ; Myocardial Reperfusion Injury ; drug therapy ; Myocytes, Cardiac ; drug effects ; Rats ; Rats, Sprague-Dawley