{"id":{"repo_id":"glasgow","oai_identifier":"oai:theses.gla.ac.uk:1164"},"canonical_url":"https://search.dev.ndltd.org/etd/glasgow/oai:theses.gla.ac.uk:1164","repository":{"repo_id":"glasgow","name":"University of Glasgow","base_url":"https://theses.gla.ac.uk/cgi/oai2"},"display":{"title":"The electrophysiological effects of Endothelin-1 in human atrial myocytes","abstract":"Introduction: Chronic heart failure (CHF) is associated with an increased incidence of atrial fibrillation (AF) and elevated levels of catecholamines and endothelin-1 (ET-1), each of which affects the atrial L-type calcium current (ICaL) and consequently action potentials. Hypotheses: ET-1 modulates the effects of isoproterenol (ISO) on ICaL and action potentials in human atrial myocytes. Methods: Atrial myocytes were isolated enzymatically from samples of right atrial appendage obtained from consenting patients in sinus rhythm undergoing cardiac surgery. The nystatin-perforated whole cell patch clamp technique was used at 37ºC to record ICaL and action potentials in voltage-clamp and current-clamp mode respectively. Results: The current-voltage relationship of ICaL was bell-shaped, peaking at +10 mV with a current density of -4.8±0.4 pA/pF (mean± s.e.m., n=89 cells, 34 patients). ISO, 0.1 nM to 1 µM, increased peak ICaL in a concentration-dependent manner (n=4-46 cells) with a maximum response of 250± 53% above control and an approximate EC50 of 0.06 µM. Isoproterenol at 0.05 µM significantly increased peak ICaL from -4.7± 0.4 to -12.2± 0.9 pA/pF (P<0.05, Students t-test; n=64 cells). This adrenergic effect was reversed by ET-1 at all concentrations tested from 0.01 to 10 nM and was partially reversible upon ET-1 washout and in the presence of the specific ET-A receptor antagonist, FR139317 (n=5-12 cells). Neither ET-1 alone nor the ET-B receptor agonist Sarafotoxin S6c, at 10 nM, had an effect on ICaL. Isoproterenol (0.05 µM) prolonged the action potential duration at 50% repolarisation (APD50) from 30± 7 to 46± 7 ms (P< 0.05, n=15 cells), but had no effect on APD90 nor the cellular ERP. These adrenergic effects on APD50 and SDs were also abolished by ET-1 at 10 nM (P< 0.05, n=15 cells). Superfusion with ET-1 (10 nM) alone had no significant effect on APD50, APD90, nor ERP (n=21 cells). There were no significant interactions between these electrophysiological effects and diseases states or chronic pre-operative drug therapy. Spontaneous activity, defined as a depolarisation occurring during phase 3 of action potential repolarisation or a depolarisation of greater than 3 mV amplitude during phase 4, frequently interrupted action potential recordings during, but not prior to, superfusion with ISO. Using a repetitive stimulation protocol, ISO at 0.05 µM produced spontaneous depolarisations in 5 of 7 cells studied (P< 0.05, chi-2 test). Endothelin-1 at 10 nM abolished these depolarisations in all 5 cells (P< 0.05). Superfusion with ET-1 (10 nM) alone was associated with spontaneous depolarisations in significantly fewer cells (P< 0.05, n=2 of 13 cells). In a retrospective univariate analysis, patient comorbidity and pre-operative drug therapy were not found to influence the electrophysiological effects observed. Conclusions: ET-1 reversed adrenergically induced increases in peak ICaL, APD50 and SDs in human atrial myocytes. This anti-adrenergic effect may be expected to influence the occurrence of AF in patients irrespective of comorbidity or pre-operative drug therapy.","abstract_html":"Introduction: Chronic heart failure (CHF) is associated with an increased incidence of atrial fibrillation (AF) and elevated levels of catecholamines and endothelin-1 (ET-1), each of which affects the atrial L-type calcium current (ICaL) and consequently action potentials. Hypotheses: ET-1 modulates the effects of isoproterenol (ISO) on ICaL and action potentials in human atrial myocytes. Methods: Atrial myocytes were isolated enzymatically from samples of right atrial appendage obtained from consenting patients in sinus rhythm undergoing cardiac surgery. The nystatin-perforated whole cell patch clamp technique was used at 37ºC to record ICaL and action potentials in voltage-clamp and current-clamp mode respectively. Results: The current-voltage relationship of ICaL was bell-shaped, peaking at +10 mV with a current density of -4.8±0.4 pA/pF (mean± s.e.m., n=89 cells, 34 patients). ISO, 0.1 nM to 1 µM, increased peak ICaL in a concentration-dependent manner (n=4-46 cells) with a maximum response of 250± 53% above control and an approximate EC50 of 0.06 µM. Isoproterenol at 0.05 µM significantly increased peak ICaL from -4.7± 0.4 to -12.2± 0.9 pA/pF (P&lt;0.05, Students t-test; n=64 cells). This adrenergic effect was reversed by ET-1 at all concentrations tested from 0.01 to 10 nM and was partially reversible upon ET-1 washout and in the presence of the specific ET-A receptor antagonist, FR139317 (n=5-12 cells). Neither ET-1 alone nor the ET-B receptor agonist Sarafotoxin S6c, at 10 nM, had an effect on ICaL. Isoproterenol (0.05 µM) prolonged the action potential duration at 50% repolarisation (APD50) from 30± 7 to 46± 7 ms (P&lt; 0.05, n=15 cells), but had no effect on APD90 nor the cellular ERP. These adrenergic effects on APD50 and SDs were also abolished by ET-1 at 10 nM (P&lt; 0.05, n=15 cells). Superfusion with ET-1 (10 nM) alone had no significant effect on APD50, APD90, nor ERP (n=21 cells). There were no significant interactions between these electrophysiological effects and diseases states or chronic pre-operative drug therapy. Spontaneous activity, defined as a depolarisation occurring during phase 3 of action potential repolarisation or a depolarisation of greater than 3 mV amplitude during phase 4, frequently interrupted action potential recordings during, but not prior to, superfusion with ISO. Using a repetitive stimulation protocol, ISO at 0.05 µM produced spontaneous depolarisations in 5 of 7 cells studied (P&lt; 0.05, chi-2 test). Endothelin-1 at 10 nM abolished these depolarisations in all 5 cells (P&lt; 0.05). Superfusion with ET-1 (10 nM) alone was associated with spontaneous depolarisations in significantly fewer cells (P&lt; 0.05, n=2 of 13 cells). In a retrospective univariate analysis, patient comorbidity and pre-operative drug therapy were not found to influence the electrophysiological effects observed. Conclusions: ET-1 reversed adrenergically induced increases in peak ICaL, APD50 and SDs in human atrial myocytes. This anti-adrenergic effect may be expected to influence the occurrence of AF in patients irrespective of comorbidity or pre-operative drug therapy.","abstract_has_math":false,"creators":["Redpath, Calum J."],"institution":"University of Glasgow","degree_name":null,"degree_level":"PhD","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2009,"date_issued":"2009","date_published":"2009","updated_at":"2026-07-24T02:23:45Z","subjects":["RM Therapeutics. Pharmacology","QP Physiology"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Redpath, Calum J."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2009"]},{"key":"dc:date.issued","label":"Date","values":["2009"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Glasgow"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://theses.gla.ac.uk/1164/"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://gla.on.worldcat.org/oclc/1547481365"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["PhD"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["RM Therapeutics. Pharmacology","QP Physiology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://theses.gla.ac.uk/1164/1/2009RedpathPhD.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Introduction: Chronic heart failure (CHF) is associated with an increased incidence of atrial fibrillation (AF) and elevated levels of catecholamines and endothelin-1 (ET-1), each of which affects the atrial L-type calcium current (ICaL) and consequently action potentials. Hypotheses: ET-1 modulates the effects of isoproterenol (ISO) on ICaL and action potentials in human atrial myocytes. Methods: Atrial myocytes were isolated enzymatically from samples of right atrial appendage obtained from consenting patients in sinus rhythm undergoing cardiac surgery. The nystatin-perforated whole cell patch clamp technique was used at 37ºC to record ICaL and action potentials in voltage-clamp and current-clamp mode respectively. Results: The current-voltage relationship of ICaL was bell-shaped, peaking at +10 mV with a current density of -4.8±0.4 pA/pF (mean± s.e.m., n=89 cells, 34 patients). ISO, 0.1 nM to 1 µM, increased peak ICaL in a concentration-dependent manner (n=4-46 cells) with a maximum response of 250± 53% above control and an approximate EC50 of 0.06 µM. Isoproterenol at 0.05 µM significantly increased peak ICaL from -4.7± 0.4 to -12.2± 0.9 pA/pF (P<0.05, Students t-test; n=64 cells). This adrenergic effect was reversed by ET-1 at all concentrations tested from 0.01 to 10 nM and was partially reversible upon ET-1 washout and in the presence of the specific ET-A receptor antagonist, FR139317 (n=5-12 cells). Neither ET-1 alone nor the ET-B receptor agonist Sarafotoxin S6c, at 10 nM, had an effect on ICaL. Isoproterenol (0.05 µM) prolonged the action potential duration at 50% repolarisation (APD50) from 30± 7 to 46± 7 ms (P< 0.05, n=15 cells), but had no effect on APD90 nor the cellular ERP. These adrenergic effects on APD50 and SDs were also abolished by ET-1 at 10 nM (P< 0.05, n=15 cells). Superfusion with ET-1 (10 nM) alone had no significant effect on APD50, APD90, nor ERP (n=21 cells). There were no significant interactions between these electrophysiological effects and diseases states or chronic pre-operative drug therapy. Spontaneous activity, defined as a depolarisation occurring during phase 3 of action potential repolarisation or a depolarisation of greater than 3 mV amplitude during phase 4, frequently interrupted action potential recordings during, but not prior to, superfusion with ISO. Using a repetitive stimulation protocol, ISO at 0.05 µM produced spontaneous depolarisations in 5 of 7 cells studied (P< 0.05, chi-2 test). Endothelin-1 at 10 nM abolished these depolarisations in all 5 cells (P< 0.05). Superfusion with ET-1 (10 nM) alone was associated with spontaneous depolarisations in significantly fewer cells (P< 0.05, n=2 of 13 cells). In a retrospective univariate analysis, patient comorbidity and pre-operative drug therapy were not found to influence the electrophysiological effects observed. Conclusions: ET-1 reversed adrenergically induced increases in peak ICaL, APD50 and SDs in human atrial myocytes. This anti-adrenergic effect may be expected to influence the occurrence of AF in patients irrespective of comorbidity or pre-operative drug therapy."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["The electrophysiological effects of Endothelin-1 in human atrial myocytes"]}]}],"canonical_facts":{"dc:creator":["Redpath, Calum J."],"dc:date":["2009"],"dc:date.issued":["2009"],"dc:description.abstract":["Introduction: Chronic heart failure (CHF) is associated with an increased incidence of atrial fibrillation (AF) and elevated levels of catecholamines and endothelin-1 (ET-1), each of which affects the atrial L-type calcium current (ICaL) and consequently action potentials. Hypotheses: ET-1 modulates the effects of isoproterenol (ISO) on ICaL and action potentials in human atrial myocytes. Methods: Atrial myocytes were isolated enzymatically from samples of right atrial appendage obtained from consenting patients in sinus rhythm undergoing cardiac surgery. The nystatin-perforated whole cell patch clamp technique was used at 37ºC to record ICaL and action potentials in voltage-clamp and current-clamp mode respectively. Results: The current-voltage relationship of ICaL was bell-shaped, peaking at +10 mV with a current density of -4.8±0.4 pA/pF (mean± s.e.m., n=89 cells, 34 patients). ISO, 0.1 nM to 1 µM, increased peak ICaL in a concentration-dependent manner (n=4-46 cells) with a maximum response of 250± 53% above control and an approximate EC50 of 0.06 µM. Isoproterenol at 0.05 µM significantly increased peak ICaL from -4.7± 0.4 to -12.2± 0.9 pA/pF (P<0.05, Students t-test; n=64 cells). This adrenergic effect was reversed by ET-1 at all concentrations tested from 0.01 to 10 nM and was partially reversible upon ET-1 washout and in the presence of the specific ET-A receptor antagonist, FR139317 (n=5-12 cells). Neither ET-1 alone nor the ET-B receptor agonist Sarafotoxin S6c, at 10 nM, had an effect on ICaL. Isoproterenol (0.05 µM) prolonged the action potential duration at 50% repolarisation (APD50) from 30± 7 to 46± 7 ms (P< 0.05, n=15 cells), but had no effect on APD90 nor the cellular ERP. These adrenergic effects on APD50 and SDs were also abolished by ET-1 at 10 nM (P< 0.05, n=15 cells). Superfusion with ET-1 (10 nM) alone had no significant effect on APD50, APD90, nor ERP (n=21 cells). There were no significant interactions between these electrophysiological effects and diseases states or chronic pre-operative drug therapy. Spontaneous activity, defined as a depolarisation occurring during phase 3 of action potential repolarisation or a depolarisation of greater than 3 mV amplitude during phase 4, frequently interrupted action potential recordings during, but not prior to, superfusion with ISO. Using a repetitive stimulation protocol, ISO at 0.05 µM produced spontaneous depolarisations in 5 of 7 cells studied (P< 0.05, chi-2 test). Endothelin-1 at 10 nM abolished these depolarisations in all 5 cells (P< 0.05). Superfusion with ET-1 (10 nM) alone was associated with spontaneous depolarisations in significantly fewer cells (P< 0.05, n=2 of 13 cells). In a retrospective univariate analysis, patient comorbidity and pre-operative drug therapy were not found to influence the electrophysiological effects observed. Conclusions: ET-1 reversed adrenergically induced increases in peak ICaL, APD50 and SDs in human atrial myocytes. This anti-adrenergic effect may be expected to influence the occurrence of AF in patients irrespective of comorbidity or pre-operative drug therapy."],"dc:format":["application/pdf"],"dc:identifier.uri":["https://theses.gla.ac.uk/1164/1/2009RedpathPhD.pdf"],"dc:language":["en"],"dc:publisher.institution":["University of Glasgow"],"dc:relation.isreferencedby":["https://theses.gla.ac.uk/1164/"],"dc:relation.isreferencedby.uri":["https://gla.on.worldcat.org/oclc/1547481365"],"dc:subject":["RM Therapeutics. Pharmacology","QP Physiology"],"dc:title":["The electrophysiological effects of Endothelin-1 in human atrial myocytes"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["PhD"]},"updated_at":"2026-07-24T02:23:45Z"}