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Department of Physiology, New York Medical College, Valhalla, New York 10595
Submitted 25 July 2002 ; accepted in final form 2 May 2003
Inhibition of endothelial nitric oxide (NO) synthase (eNOS) is associated
with an increase in glucose uptake by the heart. We have already shown that
Type I diabetes also causes a decrease in eNOS protein expression and altered
NO control of both coronary vascular resistance and oxygen consumption.
Therefore, we predict that the increase in plasma glucose and the reduction in
eNOS during diabetes together would result in a large increase in cardiac
glucose uptake. Arterial (A) and coronary sinus (C) plasma levels of glucose,
free fatty acid (FFA),
-hydroxybutyric acid (
-HBA), and lactate
were measured, and myocardial uptake was calculated before and at week 1,
2, 3, and 4 of alloxan-induced diabetes. The heart of healthy
dogs consumed FFA (19.2 ± 2.6 µeq/min) and lactate (19.7 ±
3.4 µmol/min). Dogs in the late stage of diabetes (at week 4) had
elevated arterial
-HBA concentrations (1.6 ± 0.7 µmol/l) that
were accompanied by an increased
-HBA uptake (0.3 ± 0.2
µmol/min). In contrast, myocardial lactate (4.8 ± 3.0
µmol/min) and FFA uptake (2.5 ± 1.9 µeq/min) were significantly
reduced in diabetic animals. Despite a marked hyperglycemia (449 ± 25
mg/dl), the heart did not take up glucose (7.9 ± 4.1 mg/dl). Our
results indicate significant changes in the myocardial substrate utilization
in dogs only in the late stage of diabetes, at a time when myocardial NO
production is already decreased.
lactate; free fatty acids; glucose; keto acids; myocardium
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