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Glucose metabolism, insulin effects, and developmental age of cultured neonatal rat heart cells

Cultured heart cells from 2–3 day old and 5–6 day old neonatal rats have been used as a model system for the characterization of carbohydrate metabolism in developing cardiac tissue. The rate of depletion of glucose from the growth medium was dependent on (1) the age of the animals from which the cultured cells were obtained, and (2) the presence and absence of serum and/or insulin in the growth medium. The glucose depletion rate in insulin and serumcontaining medium was 9.63 ± 0.96 nmol/min/mg protein for heart cell cultures from, 2 day old rats and 3.51 ± 0.68 nmol/min/mg protein in heart cell cultures from 5 day old rats. Appearance of lactate in the medium during these experiments occurred at the rates of 18.6 ± 7.9 nmol/min/mg and 6.4 ± 1.2 nmol/min/mg, respectively. In the absence of serum and insulin, the medium glucose depletion rates were 5.7 ± 1.6 and 2.2 ± 0.5 nmol/min/mg for cells derived from 2‐day‐old and 5‐day‐old rats, respectively. It is apparent from these data that immature cardiac cells depend upon glucose as a primary source of energy for muscle contraction and cellular growth, and that less‐efficient energy‐yielding metabolic pathways are used to obtain ATP.