Rasheda Chowdhury | Imperial College London (original) (raw)

Papers by Rasheda Chowdhury

Research paper thumbnail of Modulation of gap junctional coupling as an antiarrhythmic strategy to prevent reperfusion ventricular arrhythmias

ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to rep... more ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to reperfusion arrhythmogenesis. We tested the hypothesis that modulation of gap junctional coupling can reduce the incidence of reperfusion arrhythmias and used optical mapping to assess the mechanisms of any antiarrhythmic effect.

Research paper thumbnail of Abstract 10654: Enhancement of Gap Junctional Coupling During Acute Myocardial Infarction Reduces Inhomogeneity of Border Zone Scarring and Late Ventricular Arrhythmia Susceptibility

Circulation, Nov 22, 2011

Research paper thumbnail of Moderate gap junctional uncoupling with carbenoxolone slows conduction and increases vulnerability to ventricular arrhythmias—an optical mapping study

ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on... more ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on its own, in the absence of action potential or structural changes, is sufficient to be pro-arrhythmic. We used optical mapping: (1) to study the effects of carbenoxolone (CBX), a gap junction uncoupler, on conduction velocity and action potential duration and (2) to assess the effects of moderate conduction slowing and gap junctional uncoupling on arrhythmia vulnerability in structurally normal hearts.

Research paper thumbnail of Abstract 1258: Changes in Atrial Connexin40 and 43 are Apparent after 2 Months of Atrial Fibrillation in a Goat Model

Circulation, Oct 31, 2006

Research paper thumbnail of Relationship between connexin expression and gap-junction resistivity in human atrial myocardium

Circulation. Arrhythmia and electrophysiology, 2014

The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in dete... more The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in determining human atrial myocardial resistivity is unknown. In addressing the hypothesis that changing relative expression of Cx40 and Cx43 underlies an increase in human atrial myocardial resistivity with age, this relationship was investigated by direct ex vivo measurement of gap-junctional resistivity and quantitative connexin immunoblotting and immunohistochemistry. Oil-gap impedance measurements were performed to determine resistivity of the intracellular pathway (Ri), which correlated with total Cx40 quantification by Western blotting (rs=0.64, P<0.01, n=20). Specific gap-junctional resistivity (Rj) correlated not only with Western immunoquantification of Cx40 (rs=0.63, P=0.01, n=20), but also more specifically, with the Cx40 fraction localized to the intercalated disks on immunohistochemical quantification (rs=0.66, P=0.02, n=12). Although Cx43 expression showed no correlation with...

Research paper thumbnail of Relationship between gap-junctional conductance and conduction velocity in mammalian myocardium

Circulation. Arrhythmia and electrophysiology, 2013

Gap junction resistivity, R(j), has been proposed as a key determinant of conduction velocity (CV... more Gap junction resistivity, R(j), has been proposed as a key determinant of conduction velocity (CV). However, studies in connexin-gene knockout mice demonstrated significant CV slowing only with near-complete connexin deletion, and these findings led to the concept of a significant redundancy of myocardial gap junctions. We challenged this prevailing concept and addressed the hypothesis that there is a continuous relationship between R(j) and CV, each independently measured in human and guinea-pig myocardium. R(j) and CV were directly measured by oil-gap impedance and microelectrode techniques in human left ventricular myocardium from patients with hypertrophic cardiomyopathy and in guinea-pig atrial and ventricular myocardium before and during pharmacological uncoupling with 20-µmol/L carbenoxolone. There was a continuous relationship between R(j) and CV in human and guinea-pig myocardium, pre- and post-carbenoxolone (r(2)=0.946; P<0.01). In guinea-pig left ventricle, left atrium...

Research paper thumbnail of Moderate Gap Junctional Uncoupling with Carbenoxelone Slows Conduction and Increases Vulnerability in Ventricular Arrhythmias – An Optical Mapping Study

ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on... more ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on its own, in the absence of action potential or structural changes, is sufficient to be pro-arrhythmic. We used optical mapping: (1) to study the effects of carbenoxolone (CBX), a gap junction uncoupler, on conduction velocity and action potential duration and (2) to assess the effects of moderate conduction slowing and gap junctional uncoupling on arrhythmia vulnerability in structurally normal hearts.

Research paper thumbnail of Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model

Heart Rhythm, 2015

From the * Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingd... more From the * Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingdom, and † Imperial College London, London, SW7 2AZ, United Kingdom.

Research paper thumbnail of Modulation of Gap Junctional Coupling as an Anti-Arrhythmic Strategy to Prevent Reperfusion Ventricular Arrhythmias

ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to rep... more ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to reperfusion arrhythmogenesis. We tested the hypothesis that modulation of gap junctional coupling can reduce the incidence of reperfusion arrhythmias and used optical mapping to assess the mechanisms of any antiarrhythmic effect.

Research paper thumbnail of The contact electrogram and its architectural determinants in atrial fibrillation

The Lancet, 2013

Background The basis for the contact electrogram, the basic unit of cardiac electrophysiology, is... more Background The basis for the contact electrogram, the basic unit of cardiac electrophysiology, is only partly understood, especially in atrial fi brillation, the commonest sustained cardiac arrhythmia. We aimed to characterise the determinants of electrogram formation by electrophysiological investigation and by tissue level substrate characterisation in human and rat atrial tachycardia (AT) and atrial fi brillation (AF) using high density epicardial electrode arrays.

Research paper thumbnail of The Renin-Angiotensin System Mediates the Effects of Stretch on Conduction Velocity, Connexin43 Expression, and Redistribution in Intact Ventricle

Journal of Cardiovascular Electrophysiology, 2010

Introduction-In disease states such as heart failure, myocardial infarction and hypertrophy, chan... more Introduction-In disease states such as heart failure, myocardial infarction and hypertrophy, changes in the expression and location of Connexin43 (Cx43) occur (Cx43 remodeling), and may predispose to arrhythmias. Stretch may be an important stimulus to Cx43 remodeling; however, it has only been investigated in neonatal cell cultures, which have different physiological properties to adult myocytes. We hypothesized that localized stretch in vivo causes Cx43 remodeling, with associated changes in conduction, mediated by the renin/angiotensin system (RAS).

Research paper thumbnail of Atrial fibrillation-induced connexin 43 redistribution in atria of the goat

Heart Rhythm, 2005

Page 1. www.SCIENCEPOSTERS.co.uk Atrial fibrillation-induced Connexin 43 redistribution in atria ... more Page 1. www.SCIENCEPOSTERS.co.uk Atrial fibrillation-induced Connexin 43 redistribution in atria of the Goat Chowdhury R, Dhillon P, Kaba R, Hall MC*, Kirubakaran S*, Garratt CJ* and Peters NS Imperial College London, UK, *Manchester Heart Centre, Manchester, UK ...

Research paper thumbnail of Characteristics of Spontaneous Activity in the Bladder Trigone

European Urology, 2009

Background: During bladder filling, the trigone contracts help keep the ureteral orifices open an... more Background: During bladder filling, the trigone contracts help keep the ureteral orifices open and the bladder neck shut. The trigone generates spontaneous activity as well as responding to neuromuscular transmitters, but the relationship between these phenomena are unclear. Objectives: To characterise the cellular mechanisms that regulate and modify spontaneous activity in trigone smooth muscle. Design, setting, and participants: Muscle strips from the superficial trigone of male guinea-pigs were used for tension experiments and immunofluorescent studies. Measurements: In isolated trigonal cells, intracellular Ca 2+ was measured by epifluorescence microscopy using the fluorescent Ca 2+ indicator Fura-2. Results and limitations: Spontaneous intracellular Ca 2+ transients and contractions were observed in trigonal single cells and strips and were significantly higher compared to the bladder dome. Ca-free superfusate and verapamil terminated spontaneity. T-type Ca 2+ channel block with NiCl 2 depressed slightly Ca 2+ transients but not spontaneous contractions. Neither the BK Ca channel blocker iberiotoxin nor the SK Ca channel blocker apamin had any effect on single cell activity. By contrast, the Cl À channel blocker niflumic acid attenuated significantly both Ca 2+ transients and muscle contractions. Agonist stimulation (carbachol, phenylephrine) up-regulated activity. Gap junction labelling (Cx43) was approximately 5 times denser in the trigone than in detrusor smooth muscle. The gap junction blocker 18-ß-glycyrrhetinic acid modulated spontaneous contractions in the trigone but not in the bladder dome. Conclusions: Trigone myocytes employ membrane L-type-Ca 2+ channels and Cl À channels to generate spontaneous activity. Intercellular electrical coupling ensures its propagation and, thus, sustains contraction of the whole trigone.

Research paper thumbnail of Effects of angiotensin receptor blockade on atrial electrical remodelling and the 'second factor' in a goat burst-paced model of atrial fibrillation

Atrial fibrillation (AF) is self-perpetuating, via mechanisms of acute electrical remodelling and... more Atrial fibrillation (AF) is self-perpetuating, via mechanisms of acute electrical remodelling and 'second factors' acting over a longer time course. Renin-angiotensin system (RAS) blockade may inhibit AF self-perpetuation. We evaluated the effects of RAS blockade with candesartan in a burst-paced goat model of lone AF in which both mechanisms are known to operate. Bioactivity of oral candesartan was demonstrated in 10 goats by inhibition of the pressor effect of angiotensin II. The effects of candesartan on electrical remodelling were assessed in 12 placebo and 12 candesartan-treated goats in a 28-day burst pacing protocol. To assess the effects of candesartan on second factors (structural remodelling), 16 goats underwent further 28-day periods of burst pacing (two periods in 16 goats, three periods in eight goats) each separated by periods of sinus rhythm sufficient for electrical remodelling to reverse. There was a progressive rise in angiotensin levels in both groups. Candesartan (0.5 mg/kg/day) achieved a 76% blunting of the pressor effect of angiotensin II and had no effect on electrical remodelling; the half time for fall of atrial effective refractory period (AERP) was 22.3 ± 4.9 h (placebo) and 22.0 ± 3.2 h (candesartan) (p = ns). Candesartan had no effect on AF stability, which progressively increased over successive 28-day periods (ANOVA p < 0.05). Candesartan had no effect on atrial electrical remodelling or the operation of 'second factors' in a goat model of lone AF. These findings suggest that any benefits of RAS blockade in patients with AF are unlikely to be due to direct effects on atrial remodelling.

Research paper thumbnail of Characterisation of Connexin Expression and Electrophysiological Properties in Stable Clones of the HL-1 Myocyte Cell Line

PLoS ONE, 2014

The HL-1 atrial line contains cells blocked at various developmental stages. To obtain homogeneou... more The HL-1 atrial line contains cells blocked at various developmental stages. To obtain homogeneous sub-clones and correlate changes in gene expression with functional alterations, individual clones were obtained and characterised for parameters involved in conduction and excitation-contraction coupling. Northern blots for mRNAs coding for connexins 40, 43 and 45 and calcium handling proteins (sodium/calcium exchanger, L- and T-type calcium channels, ryanodine receptor 2 and sarco-endoplasmic reticulum calcium ATPase 2) were performed. Connexin expression was further characterised by western blots and immunofluorescence. Inward currents were characterised by voltage clamp and conduction velocities measured using microelectrode arrays. The HL-1 clones had similar sodium and calcium inward currents with the exception of clone 2 which had a significantly smaller calcium current density. All the clones displayed homogenous propagation of electrical activity across the monolayer correlating with the levels of connexin expression. Conduction velocities were also more sensitive to inhibition of junctional coupling by carbenoxolone (∼ 80%) compared to inhibition of the sodium current by lidocaine (∼ 20%). Electrical coupling by gap junctions was the major determinant of conduction velocities in HL-1 cell lines. In summary we have isolated homogenous and stable HL-1 clones that display characteristics distinct from the heterogeneous properties of the original cell line.

Research paper thumbnail of Suburothelial Myofibroblasts in the Human Overactive Bladder and the Effect of Botulinum Neurotoxin Type A Treatment

European Urology, 2009

e u r o p e a n u r o l o g y 5 5 ( 2 0 0 9 ) 1 4 4 0 -1 4 4 9 a v a i l a b l e a t w w w . s c ... more e u r o p e a n u r o l o g y 5 5 ( 2 0 0 9 ) 1 4 4 0 -1 4 4 9 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e u r o p e a n u r o l o g y . c o m

Research paper thumbnail of Modulation of gap junctional coupling as an antiarrhythmic strategy to prevent reperfusion ventricular arrhythmias

ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to rep... more ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to reperfusion arrhythmogenesis. We tested the hypothesis that modulation of gap junctional coupling can reduce the incidence of reperfusion arrhythmias and used optical mapping to assess the mechanisms of any antiarrhythmic effect.

Research paper thumbnail of Abstract 10654: Enhancement of Gap Junctional Coupling During Acute Myocardial Infarction Reduces Inhomogeneity of Border Zone Scarring and Late Ventricular Arrhythmia Susceptibility

Circulation, Nov 22, 2011

Research paper thumbnail of Moderate gap junctional uncoupling with carbenoxolone slows conduction and increases vulnerability to ventricular arrhythmias—an optical mapping study

ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on... more ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on its own, in the absence of action potential or structural changes, is sufficient to be pro-arrhythmic. We used optical mapping: (1) to study the effects of carbenoxolone (CBX), a gap junction uncoupler, on conduction velocity and action potential duration and (2) to assess the effects of moderate conduction slowing and gap junctional uncoupling on arrhythmia vulnerability in structurally normal hearts.

Research paper thumbnail of Abstract 1258: Changes in Atrial Connexin40 and 43 are Apparent after 2 Months of Atrial Fibrillation in a Goat Model

Circulation, Oct 31, 2006

Research paper thumbnail of Relationship between connexin expression and gap-junction resistivity in human atrial myocardium

Circulation. Arrhythmia and electrophysiology, 2014

The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in dete... more The relative roles of the gap-junctional proteins connexin40 (Cx40) and connexin43 (Cx43) in determining human atrial myocardial resistivity is unknown. In addressing the hypothesis that changing relative expression of Cx40 and Cx43 underlies an increase in human atrial myocardial resistivity with age, this relationship was investigated by direct ex vivo measurement of gap-junctional resistivity and quantitative connexin immunoblotting and immunohistochemistry. Oil-gap impedance measurements were performed to determine resistivity of the intracellular pathway (Ri), which correlated with total Cx40 quantification by Western blotting (rs=0.64, P<0.01, n=20). Specific gap-junctional resistivity (Rj) correlated not only with Western immunoquantification of Cx40 (rs=0.63, P=0.01, n=20), but also more specifically, with the Cx40 fraction localized to the intercalated disks on immunohistochemical quantification (rs=0.66, P=0.02, n=12). Although Cx43 expression showed no correlation with...

Research paper thumbnail of Relationship between gap-junctional conductance and conduction velocity in mammalian myocardium

Circulation. Arrhythmia and electrophysiology, 2013

Gap junction resistivity, R(j), has been proposed as a key determinant of conduction velocity (CV... more Gap junction resistivity, R(j), has been proposed as a key determinant of conduction velocity (CV). However, studies in connexin-gene knockout mice demonstrated significant CV slowing only with near-complete connexin deletion, and these findings led to the concept of a significant redundancy of myocardial gap junctions. We challenged this prevailing concept and addressed the hypothesis that there is a continuous relationship between R(j) and CV, each independently measured in human and guinea-pig myocardium. R(j) and CV were directly measured by oil-gap impedance and microelectrode techniques in human left ventricular myocardium from patients with hypertrophic cardiomyopathy and in guinea-pig atrial and ventricular myocardium before and during pharmacological uncoupling with 20-µmol/L carbenoxolone. There was a continuous relationship between R(j) and CV in human and guinea-pig myocardium, pre- and post-carbenoxolone (r(2)=0.946; P<0.01). In guinea-pig left ventricle, left atrium...

Research paper thumbnail of Moderate Gap Junctional Uncoupling with Carbenoxelone Slows Conduction and Increases Vulnerability in Ventricular Arrhythmias – An Optical Mapping Study

ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on... more ABSTRACT It is uncertain whether moderate conduction slowing through gap junctional uncoupling on its own, in the absence of action potential or structural changes, is sufficient to be pro-arrhythmic. We used optical mapping: (1) to study the effects of carbenoxolone (CBX), a gap junction uncoupler, on conduction velocity and action potential duration and (2) to assess the effects of moderate conduction slowing and gap junctional uncoupling on arrhythmia vulnerability in structurally normal hearts.

Research paper thumbnail of Fractionation of electrograms is caused by colocalized conduction block and connexin disorganization in the absence of fibrosis as AF becomes persistent in the goat model

Heart Rhythm, 2015

From the * Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingd... more From the * Manchester Heart Centre, Manchester Royal Infirmary, Manchester, M13 9WL, United Kingdom, and † Imperial College London, London, SW7 2AZ, United Kingdom.

Research paper thumbnail of Modulation of Gap Junctional Coupling as an Anti-Arrhythmic Strategy to Prevent Reperfusion Ventricular Arrhythmias

ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to rep... more ABSTRACT coupling and action potentials during early reperfusion are thought to contribute to reperfusion arrhythmogenesis. We tested the hypothesis that modulation of gap junctional coupling can reduce the incidence of reperfusion arrhythmias and used optical mapping to assess the mechanisms of any antiarrhythmic effect.

Research paper thumbnail of The contact electrogram and its architectural determinants in atrial fibrillation

The Lancet, 2013

Background The basis for the contact electrogram, the basic unit of cardiac electrophysiology, is... more Background The basis for the contact electrogram, the basic unit of cardiac electrophysiology, is only partly understood, especially in atrial fi brillation, the commonest sustained cardiac arrhythmia. We aimed to characterise the determinants of electrogram formation by electrophysiological investigation and by tissue level substrate characterisation in human and rat atrial tachycardia (AT) and atrial fi brillation (AF) using high density epicardial electrode arrays.

Research paper thumbnail of The Renin-Angiotensin System Mediates the Effects of Stretch on Conduction Velocity, Connexin43 Expression, and Redistribution in Intact Ventricle

Journal of Cardiovascular Electrophysiology, 2010

Introduction-In disease states such as heart failure, myocardial infarction and hypertrophy, chan... more Introduction-In disease states such as heart failure, myocardial infarction and hypertrophy, changes in the expression and location of Connexin43 (Cx43) occur (Cx43 remodeling), and may predispose to arrhythmias. Stretch may be an important stimulus to Cx43 remodeling; however, it has only been investigated in neonatal cell cultures, which have different physiological properties to adult myocytes. We hypothesized that localized stretch in vivo causes Cx43 remodeling, with associated changes in conduction, mediated by the renin/angiotensin system (RAS).

Research paper thumbnail of Atrial fibrillation-induced connexin 43 redistribution in atria of the goat

Heart Rhythm, 2005

Page 1. www.SCIENCEPOSTERS.co.uk Atrial fibrillation-induced Connexin 43 redistribution in atria ... more Page 1. www.SCIENCEPOSTERS.co.uk Atrial fibrillation-induced Connexin 43 redistribution in atria of the Goat Chowdhury R, Dhillon P, Kaba R, Hall MC*, Kirubakaran S*, Garratt CJ* and Peters NS Imperial College London, UK, *Manchester Heart Centre, Manchester, UK ...

Research paper thumbnail of Characteristics of Spontaneous Activity in the Bladder Trigone

European Urology, 2009

Background: During bladder filling, the trigone contracts help keep the ureteral orifices open an... more Background: During bladder filling, the trigone contracts help keep the ureteral orifices open and the bladder neck shut. The trigone generates spontaneous activity as well as responding to neuromuscular transmitters, but the relationship between these phenomena are unclear. Objectives: To characterise the cellular mechanisms that regulate and modify spontaneous activity in trigone smooth muscle. Design, setting, and participants: Muscle strips from the superficial trigone of male guinea-pigs were used for tension experiments and immunofluorescent studies. Measurements: In isolated trigonal cells, intracellular Ca 2+ was measured by epifluorescence microscopy using the fluorescent Ca 2+ indicator Fura-2. Results and limitations: Spontaneous intracellular Ca 2+ transients and contractions were observed in trigonal single cells and strips and were significantly higher compared to the bladder dome. Ca-free superfusate and verapamil terminated spontaneity. T-type Ca 2+ channel block with NiCl 2 depressed slightly Ca 2+ transients but not spontaneous contractions. Neither the BK Ca channel blocker iberiotoxin nor the SK Ca channel blocker apamin had any effect on single cell activity. By contrast, the Cl À channel blocker niflumic acid attenuated significantly both Ca 2+ transients and muscle contractions. Agonist stimulation (carbachol, phenylephrine) up-regulated activity. Gap junction labelling (Cx43) was approximately 5 times denser in the trigone than in detrusor smooth muscle. The gap junction blocker 18-ß-glycyrrhetinic acid modulated spontaneous contractions in the trigone but not in the bladder dome. Conclusions: Trigone myocytes employ membrane L-type-Ca 2+ channels and Cl À channels to generate spontaneous activity. Intercellular electrical coupling ensures its propagation and, thus, sustains contraction of the whole trigone.

Research paper thumbnail of Effects of angiotensin receptor blockade on atrial electrical remodelling and the 'second factor' in a goat burst-paced model of atrial fibrillation

Atrial fibrillation (AF) is self-perpetuating, via mechanisms of acute electrical remodelling and... more Atrial fibrillation (AF) is self-perpetuating, via mechanisms of acute electrical remodelling and 'second factors' acting over a longer time course. Renin-angiotensin system (RAS) blockade may inhibit AF self-perpetuation. We evaluated the effects of RAS blockade with candesartan in a burst-paced goat model of lone AF in which both mechanisms are known to operate. Bioactivity of oral candesartan was demonstrated in 10 goats by inhibition of the pressor effect of angiotensin II. The effects of candesartan on electrical remodelling were assessed in 12 placebo and 12 candesartan-treated goats in a 28-day burst pacing protocol. To assess the effects of candesartan on second factors (structural remodelling), 16 goats underwent further 28-day periods of burst pacing (two periods in 16 goats, three periods in eight goats) each separated by periods of sinus rhythm sufficient for electrical remodelling to reverse. There was a progressive rise in angiotensin levels in both groups. Candesartan (0.5 mg/kg/day) achieved a 76% blunting of the pressor effect of angiotensin II and had no effect on electrical remodelling; the half time for fall of atrial effective refractory period (AERP) was 22.3 ± 4.9 h (placebo) and 22.0 ± 3.2 h (candesartan) (p = ns). Candesartan had no effect on AF stability, which progressively increased over successive 28-day periods (ANOVA p < 0.05). Candesartan had no effect on atrial electrical remodelling or the operation of 'second factors' in a goat model of lone AF. These findings suggest that any benefits of RAS blockade in patients with AF are unlikely to be due to direct effects on atrial remodelling.

Research paper thumbnail of Characterisation of Connexin Expression and Electrophysiological Properties in Stable Clones of the HL-1 Myocyte Cell Line

PLoS ONE, 2014

The HL-1 atrial line contains cells blocked at various developmental stages. To obtain homogeneou... more The HL-1 atrial line contains cells blocked at various developmental stages. To obtain homogeneous sub-clones and correlate changes in gene expression with functional alterations, individual clones were obtained and characterised for parameters involved in conduction and excitation-contraction coupling. Northern blots for mRNAs coding for connexins 40, 43 and 45 and calcium handling proteins (sodium/calcium exchanger, L- and T-type calcium channels, ryanodine receptor 2 and sarco-endoplasmic reticulum calcium ATPase 2) were performed. Connexin expression was further characterised by western blots and immunofluorescence. Inward currents were characterised by voltage clamp and conduction velocities measured using microelectrode arrays. The HL-1 clones had similar sodium and calcium inward currents with the exception of clone 2 which had a significantly smaller calcium current density. All the clones displayed homogenous propagation of electrical activity across the monolayer correlating with the levels of connexin expression. Conduction velocities were also more sensitive to inhibition of junctional coupling by carbenoxolone (∼ 80%) compared to inhibition of the sodium current by lidocaine (∼ 20%). Electrical coupling by gap junctions was the major determinant of conduction velocities in HL-1 cell lines. In summary we have isolated homogenous and stable HL-1 clones that display characteristics distinct from the heterogeneous properties of the original cell line.

Research paper thumbnail of Suburothelial Myofibroblasts in the Human Overactive Bladder and the Effect of Botulinum Neurotoxin Type A Treatment

European Urology, 2009

e u r o p e a n u r o l o g y 5 5 ( 2 0 0 9 ) 1 4 4 0 -1 4 4 9 a v a i l a b l e a t w w w . s c ... more e u r o p e a n u r o l o g y 5 5 ( 2 0 0 9 ) 1 4 4 0 -1 4 4 9 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e u r o p e a n u r o l o g y . c o m