CONTRIBUTION OF D-(-)-3-HYDROXYBUTYRATE TO THE ENERGY-EXPENDITURE OF NEONATAL PIGS

In vivo oxidation rate of arterially infused D-(-)-3-hydroxybutyrate ( 3HB) was measured in 1-2-d-old-piglets. Twelve piglets (1.4 kg) were r andomly assigned to a 12 h continuous infusion of 3HB at 19.5, 37.8 55 .8 or 74.5 mu mol/min along with similar to 31 kBq/h of [3-C-14]3HB. P iglets were housed in respiration chambers allowing collection of tota l expired CO2 over 20-min intervals for the 12 h infusion and 6 h wash out. Oxidation of 3HB was calculated from the quantity and specific ra dioactivity of expired CO2 for 20-min collection periods at 6, 9 and 1 2 h for each piglet and collectively plotted against plasma 3HB concen tration measured in blood drawn during those 20-min periods. A Linewea ver-Burk plot of these data yielded a K-m of 0.62 +/- 0.07 mmol/L and V-max of 0.74 +/- 0.02 mmol ATP equivalents/(min.kg(0.75)) (parameter estimate +/- SD), which could account for 32% of the piglet mean total ATP turnover of 2.3 mmol/(min.kg(0.75)). These data show that 3HB oxi dation is a linear function of plasma concentration in the physiologic range measured in piglets (0.006 mmol/L to 0.1 mmoI/L) and within thi s range would account for 0.3% to 4.5% of piglet energy requirement. O xidation of 3HB can meet a maximum of 30 to 40% of piglet energy requi rement at unphysiologically high 3HB concentrations (>3 mmol/L).