Sex differences in the response of rat heart ventricle to calcium.
Calcium (Ca2+) is a key mediator of myocardial function. Calcium regulates contraction, and disruption of myocellular Ca2+ handling plays a role in cardiac pathologies such as arrhythmias and heart failure. This investigation examines sex differences in sensitivity of the contractile proteins to Ca2+ and myofibrillar Ca2+ delivery in the ventricular myocardium. Sensitivity of contractile proteins to Ca2+ was measured in weight-matched male and female Sprague-Dawley rats using the skinned ventricular papillary muscle fiber and Ca(2+)-stimulated Mg(2+)-dependent adenosine triphosphatase (ATPase) activity methodologies. Calcium delivery was examined by measuring the contractile response to a range of extracellular Ca2+ concentrations in isolated ventricular myocytes, papillary muscle, and the isolated perfused whole heart. Findings from studies in the whole heart suggest that at a fixed preload, the male left ventricle generates more pressure than a female ventricle over a range of extracellular Ca2+ concentrations. In contrast, results from myocyte and papillary muscle studies suggest that females require less extracellular Ca2+ to elicit a similar contractile response. Results obtained from the 2 methods used to determine sex differences in Ca2+ sensitivity were equivocal. Further studies are required to elucidate sex differences in myocardial Ca2+ handling and the reasons for disparate results in different heart muscle preparations. The results of these studies will lead to the design of sex-optimized therapeutic interventions for cardiac disease.
Schwertz
Dorie W
DW
College of Nursing M/C 802, University of Illinois, at Chicago, 845 South Damen Avenue, Chicago, IL 60612, USA. Schwertz@uic.edu
Beck
Jenny M
JM
Kowalski
Jill M
JM
Ross
James D
JD
D000704:Analysis of Variance; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006352:Heart Ventricles / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism; D010210:Papillary Muscles / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors
D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium