Myocardial energy metabolism in the hypertrophied hearts of spontaneously hypertensive rats

Abstract

Age-related changes in the myocardial energy metabolism were studied in spontaneously hypertensive (SHR) rats of 5-15 weeks of age. Systolic blood pressure increased rapidly during 5 to 10 weeks of age (developing phase) and attained a plateau level at 10 to 15 weeks (sustained phase). Even during the developing phase, the heart was hypertrophic, as assessed by an increase in the ratio of the ventricular weight to body weight. However, myocardial contents of glycolytic intermediates and high energy phosphate compounds and thus, the myocardial energy state (phosphorylation potential) in SHR rats did not differ from those in age-matched normotensive Wistar-Kyoto (WKY) rats. The lactate/pyruvate ratio was significantly lower in SHR rats. On the other hand, during the sustained phase, cardiac hypertrophy progressed only gradually, and myocardial contents of creatine phosphate and ATP were lower, while the lactate content was higher than in WKY rats. The lactate/pyruvate ratio was elevated, while phosphorylation potential was lowered. These findings suggest that the energy state is normal during the developing phase of hypertension despite the presence of cardiac hypertrophy and the increased pressure load, whereas the energy state is at a lower level during the sustained phase of hypertension.

Improved myocardial efficiency in the working perfused heart of the spontaneously hypertensive rat.

“…25 Indeed, one study in 25-week-old SHR reported a decrease in Per and an increase in myocardial lactate concentration based on findings in heart biopsy of anesthetized animals. 20 We, however, did not find any difference in the myocardial concentration of high energy metabolite or in myocardial lactate concentration even under isoproterenol stimulation. The differences between the two studies might be due to the experimental conditions.…”

Ventricular relaxation of diabetic spontaneously hypertensive rat.

“…33 Like diabd tes, LVH is associated with alterations in lipid metabolism 34 - 35 and restricted fuel source availability. 36 - 37 Elevated workloads, reduced coronary reserve, 38 and possibly increased metabolic demand for carnitine 34 (see below) may combine to predispose the hypertrophic ventricle to membranedisrupting effects of diabetes that might otherwise be less apparent in the absence of preexisting LVH.…”

Is Cardiac Hypertrophy in Spontaneously Hypertensive Rats the Cause or the Consequence of Oxidative Stress?

“…Systolic blood pressure (SBP) in SHR rapidly increases between 5 and 10 weeks of age and cardiac hypertrophy develops between 9 and 12 weeks of age (2). Increasing evidence from different experimental models supports the concept that oxidative stress contributes to the pathogenesis of myocardial hypertrophy and the process of myocardial remodeling leading to heart failure (3,4).…”