ALTERED GLUCOSE AND FATTY-ACID OXIDATION IN HEARTS OF THE SPONTANEOUSLY HYPERTENSIVE RAT

Metabolic fuel oxidation may be altered in left ventricular hypertroph y (LVH), but detailed characterizations are lacking. Although the spon taneously hypertensive rat (SHR) is a widely used experimental model o f LVH, its myocardial fuel oxidation rates are unknown. The purpose of this study was to directly measure glucose and fatty acid (FA) oxidat ion in the SHR heart: ex vivo under controlled loading conditions. Hea rts from 15-week-old SHR and Sprague Dawley (SD) rats were perfused in a recirculating system and indices of cardiac performance were contin uously monitored. The oxidation of glucose and palmitate were determin ed simultaneously at low and high workloads by the addition of U-C-14- glucose and 9,10-H-3-palmitate to the recirculating perfusate. The res ults demonstrate that FA oxidation of SHR hearts is profoundly suppres sed (60-80%) relative to that of the normotensive SD strain, particula rly at high workloads. Glucose oxidation is also moderately elevated, yielding a marked (four-to-five-fold) increase in tile ratio of glucos e/FA oxidation rates in the SHR hearts. Since more ATP is generated pe r mole of oxygen consumed when glucose is the fuel scource, these resu lts are consistent with the hypothesis that a shift away from FA use t oward glucose contributes to the preservation of energetic economy in stable, concentric LVH.