NDLI: Characteristics of intracellular $Ca^{2+}$ cycling in intact rat heart: a comparison of sex differences

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Wasserstrom, J. Andrew Kapur, Sunil Jones, Sabrina Faruque, Tania Sharma, Rohan Kelly, James E. Pappas, Amanda Ho, Wilson Kadish, Alan H. Aistrup, Gary L.
Description	Country affiliation: United States Author Affiliation: Wasserstrom JA ( Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA. ja-wasserstrom@northwestern.edu)
Abstract	Males and females show distinct differences in action potential waveform, ion channel expression patterns, and ECG characteristics. However, it is not known how sex-based differences in $Ca^{2+}$ cycling might contribute to these differences in electrophysiological activity. The goal of this study was to investigate the differences in cellular $Ca^{2+}$ transients in males and females and to examine how these might contribute to electrophysiological function. $Ca^{2+}$ transients were measured in individual myocytes within microscopic regions of the fluo-4 AM-loaded left ventricular epicardium of intact rat heart of both sexes (3 to 5 mo old). Pacing protocols were used to measure transient characteristics at a basic cycle length of 500 ms and during 10-s trains of rapid pacing delivered to the left ventricular apex. $Ca^{2+}$ transients were smaller in magnitude and longer in duration in females than in males. More importantly, the variability in $Ca^{2+}$ transient characteristics between myocytes in a microscopic recording site (heterogeneity index) was greater for females than males for characteristics related to transient duration. The rate sensitivity of $Ca^{2+}$ alternans development in individual myocytes was greater in females than in males, but there was also a greater heterogeneity in cellular responses to the rate dependence of alternans development in females. The longer $Ca^{2+}$ transients in females were also associated with slower restitution, which was likely to be responsible for the development of $Ca^{2+}$ and repolarization alternans at slower heart rates. These results demonstrate that there are distinct differences in cellular $Ca^{2+}$ cycling in male and female rat hearts. Not only is there slower reuptake of $Ca^{2+}$ in female rats, but there is greater local variability in $Ca^{2+}$ cycling at the microscopic level. These sex-based differences in $Ca^{2+}$ cycling could contribute to differences in ECG morphology and in arrhythmia sensitivity in males and females.
File Format	HTM / HTML
ISSN	03636135
e-ISSN	15221539
DOI	10.1152/ajpheart.00469.2008
Journal	AJP: Heart and Circulatory Physiology
Issue Number	5
Volume Number	295
Language	English
Publisher	American Physiological Society
Publisher Date	2008-11-01
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Discipline Physiology Discipline Cardiology Calcium Signaling Myocardium Metabolism Action Potentials Animals Arrhythmias, Cardiac Etiology Cardiac Pacing, Artificial Heart Ventricles In Vitro Techniques Kinetics Microscopy, Confocal Perfusion Pericardium Sex Factors Comparative Study Research Support, N.i.h., Extramural
Alternative Title	Characteristics of intracellular Ca2+ cycling in intact rat heart: a comparison of sex differences
Content Type	Text
Resource Type	Article
Subject	Physiology Physiology (medical) Cardiology and Cardiovascular Medicine

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