Oxidation of carbohydrates and palmitate by intact cultured neonatal rat heart cells

The rates of uptake and oxidation of glucose, lactate, pyruvate, and palmitate were measured for "mixed" cultures of rat heart cells that exhibit a myocyte-to-fibroblast ratio similar to that observed in vivo. Glucose uptake and conversion to lactate were also measured using enriched cultures of myocytes and fibroblasts. The metabolism of mixed cultures, which contain 70-80% myocytes, closely resembles that of enriched myocyte cultures. The energy production and substrate oxidation rates of cultured neonatal heart cells, adult myocytes, and perfused hearts are compared. It appears that the energy requirements of cultured heart cells are much lower than that of whole tissue. The results suggest that the metabolism of cultured heart cells may be basically the same as those in vivo but appears to be different because of reduced energy requirements in culture.