Quantitative measurements of acetoacetate metabolism and oxidation in sheep

¹ Department of Physiology, New York State Veterinary College, Cornell University, Ithaca, New York

Ketosis was produced in sheep by intravenous infusions of large quantities of acetoacetic acid (AcAc). At the infusion rates employed less than 5% was excreted in the urine. Acetoacetic acid-3-C¹⁴ was administered also as a continuous infusion to both normal and ketotic sheep. Constant plasma concentrations and specific activities were obtained and with known C¹⁴ infusion rates, several parameters of AcAc metabolism were calculated. Mean endogenous AcAc turnover rates were about 0.04 g/hr kg^3/4 (<1 g/sheep hr) but the maximal capacity of ketotic sheep to utilize AcAc was about 10-fold greater. In both normal and ketotic ewes, about one-half of the utilized AcAc was oxidized to CO₂. The percentage of the total respired CO₂ derived from AcAc metabolism increased from about 2% in normal ewes to over 30% during ketosis. The results indicate that the metabolism of ketone bodies by the normal ruminant is relatively insignificant but that, during ketosis, their contribution to the animal's total metabolism can be of major importance.

Key Words: acetoacetate turnover rates • ketone bodies • ketosis • ketone metabolism • butyrate-betahydroxy, metabolism

Submitted on April 1, 1963

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