Acetate utilization in sheep

Abstract

Rates of utilization and oxidation of acetate have been studied in sheep with [C14]acetate. The specific activity of acetate in red cells and plasma, after the addition of labelled acetate in vitro, was the same within 30 sec. of addition as after 30 min. Estimation of the utilization rate by making a single injection of isotope and following the change of specific activity with time was found unsatisfactory. Satisfactory results were obtained by constantly infusing isotope until the specific activity of plasma acetate was constant. Fasting utiliza tion rates of about 0.5 m-mole/min. were obtained. At higher plasma acetate concentrations, of the order reached after feeding, this increased to 1.8 m-moles/min. Utilization rates were altered by changes in carbo-hydrate metabolism, e.g. infusion of glucose or insulin. Both [carboxy-Cl4]acetate and [methyl-Cl4]acetate were used. Taking account of results from both, it would seem that in starved sheep about 6% of expired CO2 is derived by direct oxidation of acetate. At the higher levels found after feeding, 35% or more may be so derived.