AJP - Heart and Circulatory Physiology, Vol 243, Issue 6 884-H895, Copyright © 1982 by American Physiological Society
Estimation of rabbit myocardial metabolic rate for glucose using fluorodeoxyglucose
J. Krivokapich, S. C. Huang, M. E. Phelps, J. R. Barrio, C. R. Watanabe, C. E. Selin and K. I. Shine
The isolated arterially perfused rabbit interventricular septum was used to
determine the feasibility of using the glucose analogue
18F-2-deoxy-2-fluoro-d-glucose (DG) with a tracer kinetic model to estimate
the rate of exogenous glucose utilization. FDG was delivered to the septum
by constant infusion, and tissue 18F radioactivity was measured as a
function of time by external coincidence counting. The following four
conditions were studied: flow rates of 0.5, 1.0, and 1.5 ml/min with a
heart rate of 72 beats/min and flow at 1.5 ml/min with 96 beats/min. The
rate constants for FDG forward and reverse transport between the vascular
and extravascular compartments (k*1, k*2, respectively), phosphorylation of
FDG (k*3), and dephosphorylation of FDG-6-phosphate (FDG-6-P) (k*4) were
determined from the tissue curves using a tracer kinetic model. The lumped
constant (LC) of the deoxyglucose model calculated using Fick-derived
myocardial metabolic rates of glucose (MMRGlc), was 0.60 +/- 0.10 and was
stable over the range of conditions studied. Average k*'s and LC were used
to calculate MMRGlc's employing the model and were not significantly (P
greater than 0.05) different from those determined by the Fick method.
Tissue analyses using high-pressure liquid chromatography documented that
tissue 18F radioactivity wa due to FDG and FDG-6-P, and their relative
fractions agreed well with the values predicted from the tracer kinetic
model. Only FDG was detected in the effluent. These studies also indicate
the presence of a myocardial enzyme that can hydrolyze FDG-6-P to FDG. Thus
our results support the use of the FDG method with positron-computed
tomography for the in vivo determination of the myocardial rate of
exogenous glucose utilization.
