Results

The researchers found:

• ventricle strips from males and females had similar rates of oxygen consumption and lactate release under resting conditions;

• the inhibition of oxidative metabolism with NaCN lowered cardiac performance dramatically, and elevated resting tension and lactate release in both males and females;

• under stimulated conditions with DCA vs. controls, female ventricle strips selectively demonstrated better performance and reduced lactate release;

• force production during reoxygenation -- after a hypoxic insult -- significantly improved in males receiving DCA, but not females;

• male ventricle tissue had 2.5-fold higher citrate concentrations than females; and;

• males had a proportionately larger epicardium to endocardium ratio compared with females with similar size hearts.

Summary and Conclusions

This study expands upon previous findings that sex differences in cardiac performance and metabolism exist in fish in general, and have now been found to occur in rainbow trout in particular. Moreover, the differences are only realized during working conditions and involve stimulation or inhibition of the glycolytic pathway and carbohydrate oxidation. Ultimately, sex differences in cardiac energy metabolism and function may help define habitat suitability, swimming capabilities and health status of wild and hatchery-reared rainbow trout, and human heart disease, sex-specific treatment.