AJP - Heart and Circulatory Physiology, Vol 244, Issue 1 131-H137, Copyright © 1983 by American Physiological Society
Transmural distribution of cardiac glucose uptake in rat during physical exercise
T. E. Takala, H. J. Ruskoaho and I. E. Hassinen
The transmural distribution of glucose uptake in the left ventricle of the
heart in vivo was studied using the 2-deoxyglucose tracer method under
conditions of resting and swimming. Intravenous tracer infusion and aortic
blood sampling were performed through chronically implanted catheters. The
ventricular glucose uptake of the resting rats averaged 1.5 mumol X min-1 X
g protein-1 and was about 60% higher in the subendocardial layers than in
the superficial layers (P less than 0.01). During a 20-min swimming period
that increased the cardiac work load twofold, the glucose uptake rate was
slower (P less than 0.001), about 1.0 mumol X min-1 X g protein-1, and
evenly distributed across the left ventricular wall, whereas the reduction
in glycogen stores, also evenly distributed through the ventricular wall,
was 30 mumol glycosyl units/g protein. Blood lactate concentration
increased from 1.8 to 10-13 mM and blood glucose from 6.1 to 12 mM during
swimming, but plasma free fatty acid concentration decreased slightly. The
inhibition of glucose uptake during swimming was probably caused by the
increased use of other oxidizable substrates.
