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Sex‐based differences in cardiac contractility are evident during stress
Author(s) -
Petre Rebecca Elizabeth,
Houser Steven R,
Bailey Beth A,
Margulies Kenneth B
Publication year - 2006
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.20.5.a1448-a
Subject(s) - preload , contractility , ventricle , medicine , basal (medicine) , isometric exercise , cardiology , refractory period , heart rate , chemistry , endocrinology , hemodynamics , blood pressure , insulin
There is limited evidence that myocardial function might be different in males (M) and females, and that such differences may protect the pre‐menopausal female (F) heart from failure. We hypothesize that there are fundamental differences in calcium (Ca) regulation in cardiac myocytes of M and F that are particularly evident when assessing contractile reserve. METHODS Isometric force was measured at various frequencies (FFR) (0.5– 2.0 Hz) during either changes in bath Ca ([Ca] o ) (1.0–7.0 mM) or preload (20–100% L max ) in trabeculae(T) isolated from the right ventricle of the hearts from normal M and F cats. The resting and systolic force, time to peak force and relaxation rate was recorded for each trabeculae. RESULTS Under basal conditions (0.5 Hz, 1.75 mM Ca, 80% L max ) both M and FT achieved similar developed forces (DF) (M=10.8±1, F=10.2±1). At low rates and lengths there is no sex difference. At higher preloads and rates, there is a separation in DF in M and FT. At basal [Ca] o, both M and FT exhibited positive FFR (2.0 Hz: M=34.1±3.2, F=23.8±3.6); however, at higher [Ca] o , MT achieved greater DF (2.0 Hz, 7.0 mM Ca:M=40.1±3, F=23.7±4). CONCLUSION These data show that MT have greater developed force than FT with increased stress (i.e. pacing rate, preload, [Ca] o ). This suggests that there are fundamental sex‐based differences in cellular processes including Ca regulation and/or myofilament Ca sensitivity.