Mitochondrial Calcium Handling in Isolated Mitochondria from a Guinea Pig Heart

Mitochondrial calcium (Ca²⁺) plays a key role in regulating normal cardiac function. A physiological increase in mitochondrial matrix calcium [Ca²⁺]_m drives mitochondrial ATP production to meet the high-energy demands during excitation-contraction coupling. However, a pathological increase in [Ca²⁺]_m leads to increased oxidative stress, impaired bioenergetics, and the opening of mitochondrial permeability transition pore (mPTP), a hallmark of the failing heart. Therefore, a better understanding of the [Ca²⁺]_m handling and its role in heart function and dysfunction is of great importance. Here, we describe a detailed protocol for measuring mitochondrial Ca²⁺ handling in the isolated functionally intact mitochondria from cardiac tissue of the guinea pig.