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Sex‐based differences in the myocardial response to physiologic stress
Author(s) -
Crary Monica,
Fusco Catherine,
Barr Larry,
Bailey Beth A
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a583-d
Subject(s) - sarcomere , endocrinology , medicine , stimulation , calcium , heart rate , myocyte , chemistry , blood pressure
The female sex hormone estrogen is thought to play a protective role in the development of cardiovascular diseases in women. We hypothesize that inherent sex‐based differences in the response of the myocardium to physiologic stress may play a role in this protection. To that end, we used different pacing frequencies and the β–adrenergic agonist isoproterenol to stress isolated murine cardiac myocytes. Methods: Myocytes were isolated from male (MM) and female (FM) Swiss Webster mice, loaded with the calcium‐sensitive fluorescent dye Fluo‐3 and field‐stimulated at different pacing frequencies (0.5–4.0 Hz) on an inverted fluorescent microscope. Fluo‐3 transients and sarcomere shortening (SS) were measured at different pacing frequencies (0.5–4Hz) and after the addition of isoproterenol (ISO, 10 −7 M). Results: Under control conditions (1Hz; 1mM Ca 2+ ), SS was significantly greater (p≤.01) in MM (11.9 ±.7 % resting sarcomere length, %RSS, n=40) than in FM (8.4 ±.6 %RSS, n=36). The Rates of Shortening (ROS) and Relengthening (ROR) were also faster in MM. These differences persisted at 2, 3 and 4Hz. There was no difference in peak fluo‐3 fluorescence between MM and FM at any pacing frequency. After addition of ISO, FM experienced a significant increase in Peak fluo‐3 fluorescence and increases in contractile parameters (%RSS, ROS, ROR) that obliterated the contractile differences seen under control conditions. Conclusion: β‐adrenergic stimulation eliminated the sex‐based contractile differences seen under control conditions suggesting that FM may have a greater contractile reserve than MM.