Heat-stress responses modulate beta-adrenergic agonist and angiotensin II effects on the arrhythmogenesis of pulmonary vein cardiomyocytes.
BACKGROUND
Heat stress-induced responses reduce the occurrence of atrial fibrillation (AF). Pulmonary vein (PV) cardiomyocytes with pacemaker activity play a critical role in the pathophysiology of AF. In this study, we examined whether heat-stress responses alter the electrophysiological characteristics of PV cardiomyocytes and protect the PV against angiotensin II- or isoproterenol-induced arrhythmogenesis.


RESULTS
We used whole-cell patch clamp techniques to investigate the spontaneous activity and ionic currents in single isolated rabbit PV pacemaker cardiomyocytes with or without (control) exposure to heat stress (43°C, 15 minutes) 5 ± 1 hours before the experiments. Compared to control cardiomyocytes, heat-stressed PV cardiomyocytes had slower beating rates. Heat-stressed PV cardiomyocytes had larger L-type calcium currents, transient outward currents, smaller inward rectifier potassium currents, but similar sodium-calcium exchanger currents. Additionally, heat-stressed PV cardiomyocytes had a lower incidence of pacemaker currents than control PV cardiomyocytes. Moreover, isoproterenol increased the beating rate of control cardiomyocytes but not heat-stressed PV cardiomyocytes. Similarly, angiotensin II also increased the beating rate of control cardiomyocytes, but not heat-stressed PV cardiomyocytes, in association with decreased expression of the angiotensin II type 1 receptor.


CONCLUSIONS
Heat-stress responses altered the electrophysiological characteristics of PV cardiomyocytes and attenuated the effects of isoproterenol and angiotensin II on PV arrhythmogenesis, which may play a role in the protective potential of heat-stress responses.
Cheng
Chen-Chuan
CC
Division of Cardiology, Chi-Mei Medical Center, Tainan, Taiwan.
Huang
Chun-Feng
CF
Chen
Yao-Chang
YC
Lin
Yung-Kuo
YK
Kao
Yu-Hsun
YH
Chen
Yi-Jen
YJ
Chen
Shih-Ann
SA
D000222:Adaptation, Physiological / Q000187:drug effects; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage*; D000804:Angiotensin II / Q000008:administration & dosage*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000503:physiopathology*; D002478:Cells, Cultured; D018869:Heat-Shock Response / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects*; D011667:Pulmonary Veins / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D011817:Rabbits
D000318:Adrenergic beta-Agonists; D000804:Angiotensin II