[NAD(-STATE METABOLITES OF FREEZED-CLAMPED LIVERS OF RATS FED CASEIN OR GELATIN DIETS()] [NADH] REDOX)

Postprandial thermic effects of dietary protein meals have been hypoth esized to be related to a diet-mediated increase in amino acid oxidati on that may affect the in vivo redox states. The objective of the pres ent study was to determine the effects of isoenergetic isonitrogenous restricted (80% of the ad libitum gross energy intake) diets containin g either casein (30%) or gelatin (15% casein, and 12.7% gelatin) for 1 , 3, or 28 days to Wistar rats on liver metabolites characterizing cyt oplasmic and mitochondrial redox-states. Both casein and gelatin diets produced a progressive decline in the concentrations of lactate and a n increase in the concentrations of acetoacetate with the duration of feeding. beta-hydroxybutyrate concentrations were reduced on day 3 in relation to day 1 and were highest on day 28. Pyruvate levels changed moderately or stayed the same. The calculated redox ratios were increa sed in cytoplasm on day 3 and 28 in relation to day I and were insigni ficantly higher with the gelatin diet compared with the casein diet. T he corresponding redox ratios in mitochondria were increased on day 3 and remained high on day 28 in relation to day 1 and were significantl y higher on day 28 in the gelatin diet-fed group in relation to the ca sein diet-fed group. Adenine nucleotide content and energy charges wer e only slightly modified by the experimental conditions used. It is su ggested that these results are in accordance with a stimulation of ami no acid oxidation and reoxidation of reducing equivalents feeding the protein diets.