AJP - Endocrinology and Metabolism, Vol 240, Issue 3 253-E262, Copyright © 1981 by American Physiological Society
Validation of a tracer technique to determine nonsteady-state ketone body turnover rates in man
U. Keller, G. E. Sonnenberg and W. Stauffacher
The features of a single-compartment model of total ketone bodies were
evaluated using primed constant infusions of [3-14C]acetoacetate (AcAc) and
of D-[3-14C]beta-hydroxybutyrate (beta OHB) in 12 postabsorptive subjects.
The volume of distribution (VD) of AcAc was 0.18 +/- 0.01 liter/kg (n = 9),
and that of beta OHB was similar, 0.18 +/- 0.02 liter/kg (n = 3). The
production rate of total ketone bodies was calculated using the combined
specific activity of AcAc and of beta OHB. The mean basal total ketone body
production rates were similar using either [14C]AcAc (6.5 mumol . kg-1 .
min-1) or [14C]beta OHB (6.8 mumol . kg-1 . min-1). To determine the pool
fraction that was rapidly mixed during nonsteady state of ketone body
inflow, unlabeled AcAc was infused with stepwise increasing and decreasing
rates between 5 and 25 mumol . kg-1 . m-1 to mimic nonsteady-state ketone
body production rates. The "functional" pool fraction P was determined as
the pool fraction that provided the best match between tracer-determined
rates of ketone production and rates of AcAc infusion. P of total ketone
bodies was almost equal to 1 using either [14C]AcAc (1.05 +/- 0.16) or
[14C]beta OHB (1.00 +/- 0.06), suggesting rapid mixing of ketone bodies
throughout the entire pool. The described pool model may be used to
determine total ketone body kinetics during acute perturbations of the
steady state.
