Overexpression of histidine-rich calcium binding protein in equine ventricular myocardium.

Histidine-rich calcium binding protein (HRC) is a high capacity, low affinity Ca2+ binding protein, specifically expressed in striated muscles of mammals. In rabbit skeletal and cardiac muscles, HRC binds to sarcoplasmic reticulum (SR) membranes via triadin, a junctional SR protein. Recently, a potential role in heart failure and arrhythmogenesis has been assigned to HRC due to its activity as regulator of SR Ca2+ uptake and Ca2+ release. HRC might play a particularly relevant role in the equine heart, given its slower resting heart rate (20–35beats/min) and longer action potential duration (APD) (0.6–1.0s) than are found in other mammals.