Effects of thienopyridines and thienopyrimidinones on L-type calcium current in isolated cardiomyocytes.

Thienopyridines (ticlopidine, clopidogrel) are frequently used drugs in antiplatelet therapy and have been shown to exert a more pronounced negative inotropic effect than thienopyrimidinones. We hypothesized that these differences are due to a differential impact of thienopyridines and thienopyrimidinones on L-type calcium current at the single-cell level. The effects of thienopyridines and thienopyrimidinones were studied on L-type calcium current and action potential parameters with the whole-cell patch-clamp technique in isolated myocytes from guinea pig ventricle and human atrial appendage.

Impaired regulation of cardiac function in sepsis, SIRS, and MODS.

In sepsis, systemic inflammatory response syndrome (SIRS), and multiorgan dysfunction syndrome (MODS), a severe prognostically relevant cardiac autonomic dysfunction exists, as manifested by a strong attenuation of sympathetically and vagally mediated heart rate variability (HRV). The mechanisms underlying this attenuation are not limited to the nervous system. They also include alterations of the cardiac pacemaker cells on a cellular level.

Endotoxin impairs the human pacemaker current If.

LPSs trigger the development of sepsis by gram-negative bacteria and cause a variety of biological effects on host cells, including alterations on ionic channels. Because heart rate variability is reduced in human sepsis and endotoxemia, we hypothesized that LPS affects the pacemaker current I(f) in human heart, which might--at least in part--explain this phenomenon. Isolated human myocytes from right atrial appendages were incubated for 6 to 10 h with LPS (1 and 10 microg/mL) and afterwards used to investigate the pacemaker current I(f).

Oxidized LDL induces ventricular myocyte damage and abnormal electrical activity--role of lipid hydroperoxides.

Objective: It was our aim to investigate effects of human LDL, copper-, or AAPH-oxidized over different periods of time to different degrees (ox-LDL), on viability and electrophysiological parameters of isolated ventricular myocytes of guinea pigs.

Methods: Guinea pig ventricular myocytes were incubated with ox-LDL or native LDL (at 0.5 mg/ml) for 12 h, and afterwards myocyte damage, action potentials, and transmembrane ion currents were studied (at 37 degrees C).

An ionic model for rhythmic activity in small clusters of embryonic chick ventricular cells.

We recorded transmembrane potential in whole cell recording mode from small clusters (2-4 cells) of spontaneously beating 7-day embryonic chick ventricular cells after 1-3 days in culture and investigated effects of the blockers D-600, diltiazem, almokalant, and Ba2+. Electrical activity in small clusters is very different from that in reaggregates of several hundred embryonic chick ventricular cells, e.g.

If in left human atrium: a potential contributor to atrial ectopy.

Objective: The left human atrium plays an important role in initiation of atrial fibrillation (AF) and the hyperpolarization activated cation current (I(f)) is a candidate for contributing to abnormal automaticity. However, electrophysiological data concerning I(f) are not available in this cardiac region and we therefore investigated I(f) in human left atrial tissue.

Methods: Human atrial myocytes were isolated from the left atrial appendage (LAA) and the left atrial wall (LAW) obtained from patients undergoing open heart surgery.

L-type and T-type Ca2+ current in cultured ventricular guinea pig myocytes.

The aim of this investigation was to study L-type and T-type Ca(2+) current (I(CaL) and I(CaT)) in short-term cultured adult guinea pig ventricular myocytes. The isolated myocytes were suspended in serum-supplemented medium up to 5 days. Using whole-cell patch clamp techniques ICaL and ICaT were studied by applying voltage protocols from different holding potentials (-40 and -90 mV).

Influence of preservatives and topical steroids on ciliary beat frequency in vitro.

Objective: To measure the influence of topical steroids and the preservative potassium sorbate on the ciliary beat frequency (CBF) of human nasal mucosa in vitro.

Design: In vitro study of cultured ciliated cells of human nasal mucosa.

Methods: Human nasal mucosa was removed endoscopically and cultured for 10 days.

A hyperpolarization activated inward current (If) is present in infant ventricular myocytes.

I(f) was shown to be present in adult human atrial and ventricular myocytes but data obtained from infant myocytes are lacking. We have studied I(f) in isolated ventricular myocytes from children undergoing surgical correction of tetralogy of Fallot (TOF; n = 5; mean age: 15.3 months).

NADH supplementation decreases pinacidil-primed I K ATP in ventricular cardiomyocytes by increasing intracellular ATP.

1 The aim of this study was to investigate the effect of nicotinamide-adenine dinucleotide (NADH) supplementation on the metabolic condition of isolated guinea-pig ventricular cardiomyocytes. The pinacidil-primed ATP-dependent potassium current I(K(ATP)) was used as an indicator of subsarcolemmal ATP concentration and intracellular adenine nucleotide contents were measured. 2 Membrane currents were studied using the patch-clamp technique in the whole-cell recording mode at 36-37 degrees C.

Selectivity of different calcium antagonists on T- and L-type calcium currents in guinea-pig ventricular myocytes.

Both L- and T-type calcium channels are present in the heart. In cardiac myocytes L-type calcium channels are blocked by the classical calcium channel blockers, while T-type calcium channels are thought to be insensitive to these drugs and to be selectively blocked by mibefradil. We aimed to compare the T/L calcium channel blocking selectivity of several calcium channel blockers by evaluating their effects on both components evoked in the same cell from a holding potential corresponding to the normal physiological value (-90mV).

Effects of K+ channel openers on I K(ATP) of human atrial myocytes at physiological temperatures.

The aim of this study was to investigate the effects of the potassium channel openers (PCOs) cromakalim and pinacidil on the ATP-dependent potassium current I(K)(ATP) in human atrial myocytes. Cells were isolated from the right atrial appendage obtained during cardiac surgery. Membrane currents were studied with the patch-clamp technique in the whole-cell recording mode at 36 degrees -37 degrees C.

In human hypercholesterolemia increased reactivity of vascular smooth muscle cells is due to altered subcellular Ca(2+) distribution.

There is evidence that, besides an attenuated endothelium-dependent relaxation, functional changes in smooth muscle contractility occur in experimental hypercholesterolemic animals. Unfortunately, little is known of the situation in human arteries, and the intracellular mechanisms involved in the modulation of vascular smooth muscle function in human hypercholesterolemia are still unclear. Thus, besides acetylcholine-induced endothelium-dependent relaxation, smooth muscle reactivity to KCl, norepinephrine (NE) and phenylephrine (PE) was evaluated in uterine arteries from 34 control individuals (CI) and 22 hypercholesterolemic patients (HC).

The sulphonylurea glibenclamide inhibits voltage dependent potassium currents in human atrial and ventricular myocytes.

1 It was the aim of our study to investigate the effects of the sulphonylurea glibenclamide on voltage dependent potassium currents in human atrial myocytes. 2 The drug blocked a fraction of the quasi steady state current (ramp response) which was activated positive to -20 mV, was sensitive to 4-aminopyridine (500 microM) and was different from the ATP dependent potassium current IK(ATP). 3 Glibenclamide dose dependently inhibited both, the peak as well as the late current elicited by step depolarization positive to -20 mV.

Repolarizing currents in ventricular myocytes from young patients with tetralogy of Fallot.

Objective: It was the aim of our study to describe repolarizing currents in ventricular myocytes isolated from children with tetralogy of Fallot. This is the first report on outward currents in ventricular myocytes from children.

Methods: Ventricular myocytes were isolated from tissue samples of the outflow tract of the right ventricle which were obtained during corrective surgery of tetralogy of Fallot.

Human diabetes is associated with hyperreactivity of vascular smooth muscle cells due to altered subcellular Ca2+ distribution.

Alterations of vascular smooth muscle function have been implicated in the development of vascular complications and circulatory dysfunction in diabetes. However, little is known about changes in smooth muscle contractility and the intracellular mechanisms contributing to altered responsiveness of blood vessels of diabetic patients. Therefore, smooth muscle and endothelial cell function were assessed in 20 patients with diabetes and compared with 41 age-matched control subjects.

L-type calcium current in human ventricular myocytes at a physiological temperature from children with tetralogy of Fallot.

Objective: The aim was to investigate the electrophysiological properties of the L-type calcium current (ICa,L) in ventricular myocytes at a physiological temperature (36-37 degrees C) isolated from children undergoing surgical repair of tetralogy of Fallot.

Methods: ICa,L was recorded with the patch-clamp technique in the single electrode whose-cell mode at a physiological calcium concentration (1.8 mmol/l) at 36-37 degrees C.

Estimation of outward currents in isolated human atrial myocytes using inactivation time course analysis.

The aim was to investigate outward currents in single, isolated, human, atrial myocytes and to determine the relative contribution of individual current components to the total outward current. Currents were recorded using the whole-cell patch-clamp technique at 36-37 degreesC. Individual outward current components were estimated from recordings of total outward current using a mathematical procedure based on the inactivation time course of the respective currents.

[Effect of topical corticosteroids and topical antihistaminics on ciliary epithelium of human nasal mucosa in vitro].

A normal ciliary beat frequency of ciliated cells is necessary for the mucociliary clearance of the nose and paranasal sinuses. An in vitro investigation was performed to evaluate the influence of topical corticosteroids and antihistamines on the ciliary beat frequency of human nasal mucosa. The nasal sprays examined contained the corticosteroids budesonide or fluticasone propionate and the topical antihistamines azelastine or levocabastine.

The pacemaker current I(f) in single human atrial myocytes and the effect of beta-adrenoceptor and A1-adenosine receptor stimulation.

1. We used single human atrial myocytes to study I(f) occurrence, properties and pharmacological modulation. Cells were obtained by chunk enzymatic digestion from samples of right atrial appendages of patients undergoing corrective cardiac surgery.

A novel benzothiazine Ca2+ channel antagonist, semotiadil, inhibits cardiac L-type Ca2+ currents.

The influence of semotiadil fumarate, a novel vasoselective Ca2+ channel antagonist with a benzothiazine skeleton, was measured on the high-threshold Ca2+ current ICa,L in guinea-pig ventricular myocytes prepared by coronary perfusion with collagenase solution. Patch- and voltage-clamp methods were used to measure ICa,L. Diltiazem, nifedipine and amlodipine were studied for comparison.

Xenoreactive natural antibodies and induced antibodies--their effects of beating cardiomyocytes as a model of a xenograft.

Xenotransplantation has been complicated by hyperacute rejection reactions, which are supposedly triggered by preformed natural antibodies (PNAb) of the recipient organism, whereas the role of antibodies specifically induced by previous antigen contact (IAb) is less clear. Primary cultures of spontaneously beating neonatal rat cardiomyocytes were used as a model of the heart to elaborate the effects of both PNAb and IAb from xenogeneic species and to investigate into their mechanisms of action. An experimental setup allowing for rapid medium exchange under continuous observation was employed.

Different action of xenoreactive natural and immune antibodies on functioning cardiomyocytes.

PNAB and IAB have totally different action on BCM. PNAB inhibit the contractile function of BCM by producing a reversible standstill and by disturbing the synchronization of the BCM-monolayer. IAB are cytotoxic and depend on the presence of complement.

Effects of the class III antiarrhythmic drug ambasilide on outward currents in human atrial myocytes.

We have studied the inhibitory influence of the class III antiarrhythmic drug ambasilide (LU 47110) on the transient outward current Ito1 and the sustained current Iso following inactivation of Ito1, in human atrial myocytes. The two currents are separated by a mathematical procedure based on the amplitudes and time constants of the biexponential inactivation of the total outward current. The frequency dependence, the recovery from inactivation and the kinetics of activation and inactivation are described.

[In vitro studies of the effect of vasoconstrictor nose drops on ciliary epithelium of human nasal mucosa].

We investigated the influence of four nasal decongestants and one preservative on ciliated cells, using cell cultures of human nasal mucosa. These cells were exposed to nasal decongestants in vitro. A fast decrease in ciliary beat frequency was seen during naphazoline and oxymethazoline application which was fully reversible after naphazoline.