Factors affecting acetoacetate production rates by normal and ketotic pregnant sheep

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Abstract
The effects of the administration of insulin, growth hormone, glucose, propionic acid, and butyric acid on endogenous acetoacetic acid (AcAc) production rates and plasma AcAc concentrations were studied in 15 experiments on 12 unanesthetized normal or ketotic pregnant ewes. AcAc production was measured by the isotope-dilution method involving a constant intravenous infusion of AcAc-3-C14. Insulin, glucose, and propionic acid injection markedly reduced AcAc production rates and plasma AcAc concentrations within 1/2 hr. Butyric acid produced opposite effects; about one-fifth was converted to ketone bodies. Growth hormone produced no consistent effects. In all experiments, the plasma AcAc concentration increased or decreased with concomitant changes in AcAc production. It is concluded that, up to a plasma AcAc concentration of about 10 mg/100 ml, ketone-body concentrations in the bloodstream merely are a reflection of the rate of ketone-body production and that utilization, in turn, is dependent upon blood ketone concentrations. It was shown previously that a steady maximal rate of AcAc utilization occurs at plasma AcAc concentrations greater than about 10 mg/100 ml.