Whole-Body, Peripheral and Intestinal Endogenous Acetate Turnover in Dogs Using Stable Isotopes ,

Abstract

Acetate metabolism supplies about 10% of energy requirements in food-deprived nonruminant animals. This study used a stable isotope dilution method to investigate the fate of acetate in 24-h food-deprived dogs free of colonic fermentation. Three dogs received intravenous bolus injections of 40 or 70 μmol/kg of [1-13C] acetate, and carotid blood was then sampled during a 15-min period to estimate the acetate distribution volume. Ten dogs received intravenous [1-13C] acetate infusions of 1.05 ± 0.02 or 2.10 ± 0.10 μmol/(kg⋅min) for 120 or 200 min after a prime of 200 or 70 μmol/kg, respectively. Cephalic venous and carotid arterial blood were sampled for all dogs, and portal blood for five. Acetate distribution volume was 0.27 ± 0.16 L/kg (mean ± SEM). The concentrations of acetate in arterial (144 ± 17 μmol/L), venous (155 ± 20 μmol/L) and portal plasma (131 ± 16 μmol/L) were not significantly different during infusion, whereas isotopic enrichments [mole percent excess (MPE): labeled acetate/all acetate molecules] in portal (1.2 ± 0.2 MPE) and venous plasma (1.7 ± 0.3 and 2.6 ± 0.7 MPE) were lower than in arterial plasma for both infusion rates (4.9 ± 0.6 and 7.6 ± 0.8 MPE, respectively, P< 0.005). Whole-body acetate turnover was 24.4 ± 2.4 μmol/(kg⋅min). Fractional acetate extractions for forelimb and intestine were 62 ± 7 and 72 ± 6%, respectively, and the production for each organ was 0.3 and 1.1 μmol/(kg⋅min) respectively, similar to that of utilization (P> 0.05). It is concluded that the forelimb and intestine produce and utilize acetate as an energy source in 24-h food-deprived dogs free of colonic fermentation.