Contribution of viable and nonviable heart myocytes to substrate oxidation

An approach is described that allows metabolic data obtained from a mixture of vital dye-excluding (T-) and nonexcluding (T+) myocytes to be extrapolated to a homogeneous cell population. Myocytes from adult dog hearts were dispersed by enzymatic treatment and separated into two fractions: one containing predominantly T-, and the other containing predominately T+ cells. Measuring the oxidation rate and viability of each fraction allows the determination of the rate of oxidation of a homogeneous cell population when palmitate, glucose, or lactate is the oxidizable substrate. The calculated rate of oxidation of these substrates by 100% T- cells was: 0.15, 0.46, and 2.99 nmol . mg protein-1 . min-1, respectively. Oxidation of palmitate and lactate by T+ cells was one-fifth of the T-cell rate. Glucose oxidation of T+ cells was not significantly different from zero. Use of this procedure will permit study of myocardial metabolism when experimental procedures may cause altered cell viability.