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 Ca2+-stimulated Mg2+-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. I...