Diverse cell morphology and intracellular calcium dynamics in pulmonary vein cardiomyocytes.
Pulmonary veins (PVs) contain cardiomyocytes with a complex cellular morphology and high arrhythmogenesis. Ca(2+) regulation and Ca(2+) sparks play a pivotal role in the electrical activity of cardiomyocytes. The purpose of this study was to investigate whether the cell morphology can determine the PV electrical activity and Ca(2+) homeostasis. Through confocal microscopy with fluo-3 Ca(2+) fluorescence, Ca(2+) sparks and Ca(2+) transients were evaluated in isolated single rabbit left atria (LA) and PV cardiomyocytes according to the cell morphology (rod, rod-spindle and spindle/bifurcated). Twenty-two (20%) rod, 49 (43%) rod-spindle and 41 (37%) spindle/bifurcated cardiomyocytes were identified in the LA (n = 29) and PV (n = 83) cardiomyocytes. The PV cardiomyocytes with pacemaker activity had a higher incidence of spindle/bifurcated morphology than LA and PV cardiomyocytes without pacemaker activity. As compared to those in the rod or rod-spindle cardiomyocytes, spindle/bifurcated cardiomyocytes had a larger Ca(2+) transient amplitude and higher frequency of the Ca(2+) sparks with larger amplitude and longer duration. In contrast, rod-spindle and rod cardiomyocytes had similar Ca(2+) transients and Ca(2+) sparks. The cell length correlated well with the amplitude of the Ca(2+) transient and Ca(2+) spark duration with a linear regression. In conclusion, cell morphology and cell length play a potential role in the Ca(2+) homeostasis and Ca(2+) spark. The large Ca(2+) transients and high frequency of Ca(2+) sparks in spindle/bifurcated cardiomyocytes may cause a high arrhythmogenesis in the PV cardiomyocytes with pacemaker activity.
Yu
Ming-Chih
MC
Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan.
Huang
Chun-Feng
CF
Chang
Che-Ming
CM
Chen
Yao-Chang
YC
Lin
Cheng-I
CI
Chen
Shih-Ann
SA
D000704:Analysis of Variance; D000818:Animals; D001683:Biological Clocks; D020013:Calcium Signaling; D048430:Cell Shape; D006325:Heart Atria / Q000166:cytology / Q000378:metabolism; D006339:Heart Rate; D066298:In Vitro Techniques; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011667:Pulmonary Veins / Q000166:cytology / Q000378:metabolism*; D011817:Rabbits; D013997:Time Factors