Ketone body metabolism in chickens

Abstract

1. 1. Acetoacetate and β-hydroxybutyrate concentrations in rat, guinea-pig, and chicken blood were 0.066, 0.045, and 0.064 μmole and 0.142, 0.021, and 0.446 μmole per ml. respectively. 2. 2. Liver mitochondria from the animals produced acetoacetate and β-hydroxybutyrate from palmitoyl- l-carnitine; 72, 56, and 108 μmoles and 6.0, 2.9, and 0.8 nmoles per 20 minutes per mg. protein respectively. 3. 3. Fasting elevated acetoacetate and β-hydroxybutyrate levels by ten- to twelvefold in rat and guinea-pig blood, whereas only 20 per cent and 90 per cent increases were noted in chicken blood under similar conditions. Fasting altered acetoacetate production in rats and guinea-pigs by 20 per cent and 18 per cent but did not alter the production of this ketone body in chickens. On the other hand, β-hydroxybutyrate production was not affected in any species by fasting. 4. 4. Refeeding the fasting animals with their normal diets for 48 hours brought back their ketone body concentrations and productions to nearly normal levels. 5. 5. The utilization of acetyl CoA (a product of fatty acid degradation) by chickens for energy production via the tricarboxylic acid cycle, in preference to the formation to ketone bodies prior to utilization (as is the case with rats), is discussed.