Sex differences in volume overload in skinned fibers

Area of Science:

• Cardiovascular Physiology
• Cardiac Muscle Mechanics
• Sex Differences in Cardiovascular Disease

Background:

• Cardiac morphology and function in chronic volume overload are sex-dependent.
• Actin-myosin level contractile properties related to sex in this condition remain undefined.

Purpose of the Study:

• To investigate the influence of sex on cardiac contractile properties at the actin-myosin level in patients with chronic volume overload.
• To compare force generation and calcium sensitivity between male and female cardiac fibers.

Main Methods:

• Right auricle myocardial samples were obtained from 36 patients (18 males, 18 females) undergoing mitral valve surgery for severe mitral regurgitation.
• Skinned cardiac fibers were subjected to varying calcium concentrations to measure calcium-induced force development.
• Calcium sensitivity of the fibers was assessed.

Main Results:

• Female cardiac fibers exhibited greater force generation at maximal calcium concentrations (pCa 4.0) compared to male fibers.
• Male cardiac fibers showed higher force generation at mean calcium concentrations.
• Calcium sensitivity differed significantly between sexes, with males demonstrating higher sensitivity.

Conclusions:

• Female cardiac fibers develop higher maximal force, potentially utilizing full force potential.
• Male cardiac fibers exhibit higher calcium sensitivity, possibly compensating for lower maximal force.
• These findings suggest sex-specific differences in cardiac contractility and energy efficiency in chronic volume overload, particularly in mitral regurgitation.