Characteristics of intracellular Ca2+ cycling in intact rat heart: a comparison of sex differences
| Autor: | Sunil Kapur, Alan H. Kadish, Gary L. Aistrup, Tania Faruque, James E. Kelly, J. Andrew Wasserstrom, Wilson C. Ho, Sabrina Jones, Amanda Pappas, Rohan Sharma |
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| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
Male
medicine.medical_specialty Physiology Heart Ventricles Action Potentials Biology In Vitro Techniques Reuptake Sex Factors Physiology (medical) Internal medicine medicine Repolarization Left Ventricular Epicardium Myocyte Animals Calcium Signaling Microscopy Confocal Myocardium Cardiac Pacing Artificial Arrhythmias Cardiac T wave alternans Articles Rats Perfusion Electrophysiology Kinetics Endocrinology Circulatory system Female Cardiology and Cardiovascular Medicine Pericardium |
| Popis: | 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 Ca2+ cycling might contribute to these differences in electrophysiological activity. The goal of this study was to investigate the differences in cellular Ca2+ transients in males and females and to examine how these might contribute to electrophysiological function. Ca2+ 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. Ca2+ transients were smaller in magnitude and longer in duration in females than in males. More importantly, the variability in Ca2+ 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 Ca2+ 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 Ca2+ transients in females were also associated with slower restitution, which was likely to be responsible for the development of Ca2+ and repolarization alternans at slower heart rates. These results demonstrate that there are distinct differences in cellular Ca2+ cycling in male and female rat hearts. Not only is there slower reuptake of Ca2+ in female rats, but there is greater local variability in Ca2+ cycling at the microscopic level. These sex-based differences in Ca2+ cycling could contribute to differences in ECG morphology and in arrhythmia sensitivity in males and females. |
| Databáze: | OpenAIRE |
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