WHOLE-BODY, PERIPHERAL AND INTESTINAL ENDOGENOUS ACETATE TURNOVER IN DOGS USING STABLE ISOTOPES

Acetate metabolism supplies about 10% of energy requirements in food-d eprived 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 in jections of 40 or 70 mu mol/kg of [1-C-13] acetate, and carotid blood was then sampled during a 15-min period to estimate the acetate distri bution volume. Ten dogs received intravenous [1-C-13] acetate infusion s of 1.05 +/- 0.02 or 2.10 +/- 0.10 mu mol/(kg . min) for 120 or 200 m in after a prime of 200 or 70 mu mol/kg, respectively. Cephalic venous and carotid arterial blood were sampled for all dogs, and portal bloo d for five. Acetate distribution volume was 0.27 +/- 0.16 L/kg (mean /- SEM). The concentrations of acetate in arterial (144 +/- 17 mu mol/ L), venous (155 +/- 20 mu mol/L) and portal plasma (131 +/- 16 mu mol/ L) were not significantly different during infusion, whereas Isotopic enrichments [mole percent excess (MPE): labeled acetate/all acetate mo lecules] in portal (1.2 +/- 0.2 MPE) and venous plasma (1.7 +/- 0.3 an d 2.6 +/- 0.7 MPE) were lower than in arterial plasma for both infusio n rates (4.9 +/- 0.6 and 7.6 +/- 0.8 MPE respectively, P < 0.005). Who le-body acetate turnover was 24.4 +/- 2.4 mu mol/(kg . min). Fractiona l 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 mu mol/(kg . min) respectively, similar to that of utilization (P > 0.05). It is concluded that the forelimb and intestine produce and uti lize acetate as an energy source in 24-h food-deprived dogs free of co lonic fermentation.