Cardiac taurine deficiency reduces sarcoplasmic reticular Ca 2+-ATPase activity in mammals and our results are consistent with such an effect in rainbow trout. In isometrically contracting ventricular strip preparations, the force–frequency and extracellular Ca 2+-sensitivity relationships were both shifted downward and maximum pacing frequency was significantly lower in β-alanine fed trout. Taurine deficiency did not affect routine or maximum rates of O 2 consumption, aerobic scope, or critical swimming speed in whole animals but cardiac contractility was significantly impaired. Cardiac taurine was reduced by 17% after 4 weeks with no effect on growth or condition factor. We addressed this gap in knowledge by generating a taurine-deficient rainbow trout ( Oncorhynchus mykiss) model using a feed enriched with 3% β-alanine to inhibit cellular taurine uptake. In fish, cardiac taurine levels vary substantially between species and can decrease by up to 60% in response to environmental change but its contribution to cardiac function is understudied. Taurine deficiency is rare in mammals, where it impairs cardiac contractility and leads to congestive heart failure. Taurine is a non-proteinogenic sulfonic acid found in high concentrations inside vertebrate cardiomyocytes and its movement across the sarcolemmal membrane is critical for cell volume regulation.
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