The redox state and the concentration of ketone bodies in tissues of rats fed carbohydrate free diets.

The effect of carbohydrate free-low protein diets on the redox potential and ketone body concentrations in liver, muscle, and blood was investigated. Two carbohydrate free diets were fed: 1) A diet in which all the non-protein energy was provided by fatty acids (FA); 2) A similar diet in which the fatty acids were substituted by neutral fat (NF). A carbohydrate rich diet (HC) was fed for comparison. The redox potentials in cytoplasma and mitochondria were calculated from the relative concentrations of the [lactate]:[pyruvate] and [beta-hydroxy-butyrate]:[acetoacetate] couples respectively. In fed rats the cytoplasmic redox potential in liver was much higher in FA than in NF rats, but in fasted NF rats it increased markedly and equaled that of FA rats. In liver mitochondria the redox potential was lower in fed FA than in fed NF rats, while after a 24 hour fast it increased in FA rats and decreased in NF rats. Total ketone body concentrations were high in fed NF rats and increased further in fasted rats, however, in FA rats the high concentrations in the fed state decreased after the short fast. The changes of total ketone-bodies in blood and muscle followed those in liver in both fed and fasted states.