[4] Isolation of mitochondria with emphasis on heart mitochondria from small amounts of tissue

The fibrous structure of muscle tissue and the contaminating collagenous material around the fibers create particular problems for the isolation of heart mitochondria. Although the isolation method does not significantly differ from the methods used for other tissues, special attention must be paid to the problem of tissue homogenization. The high Ca2+ content of the heart tissue and the characteristics of Mg2+ binding in heart mitochondria require special treatment. Proper composition of the isolation medium is crucial. It might be advantageous to supplement the isolation medium with a high concentration of adenosine triphosphate (ATP). However, because of the high cost of ATP, this has not been done. In addition to the use of small laboratory animals, it is feasible to isolate good mitochondrial preparations from small samples of human heart muscle, which are readily available from children or adults during open heart operations. Usually, samples larger than one gram of tissue cannot be obtained. Often, 0.5 grams must suffice. This method has been used successfully for the isolation of heart mitochondria from several species of adult and newborn animals as well as human samples.