Effect of pressure development on membrane transport of glucose in isolated rat heart

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Abstract
Glucose uptake by the perfused rat heart was measured over a range of left ventricular pressure development. Extracellular transfer of glucose, the 1st step in the uptake process, restricted uptake by less than 20% at moderate rates of pressure development and physiological glucose concentrations. Membrane transport was the major rate-limiting step for glucose uptake and was progressively accelerated as the ventricle developed more pressure. L-Arabinose transport was also stimulated. Between 93 and 98% of the transport activity was regulated by mechanical activity. A kinetic evaluation of the effect of pressure development indicated that the Vmax of transport was increased. In addition) trans port was more sensitive to stimulation by insulin in hearts developing more pressure. Glucose phosphorylation was stimulated when pressure development was increased, resulting in a low intracellular free glucose concentration although membrane transport was accelerated. When glucose was the only exogenous nutrient provided, oxidation of the glucose and glycogen that were consumed would have required about 30% of the O2 uptake at low rates of pressure development and as much as 84% at high rates.