Alterations of energy metabolism in the spontaneously hypertensive rat: a 31P nuclear magnetic resonance study.

We quantified high-energy phosphate metabolites in hypertensive hypertrophied and normal myocardium and monitored temporal changes using the non-invasive 31P nuclear magnetic resonance (NMR) spectroscopy. Hearts from 18 month spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) were perfused with a phosphate-free buffer at 10 cc/min per g and paced at 240 beats/min on a modified Langendorff apparatus. Perfusion pressure, left ventricular pressure (LVP) and dP/dt were recorded and successive 31P NMR spectra were collected during a 24-min baseline period (oxygenated buffer), anoxia (N2-bubbled and glucose-free buffer) until a 70% fall in LVP occurred, and recovery. An aminomethylphosphonate standard, located within the LVP balloon, permitted absolute quantification of myocardial phosphate moieties (including inorganic phosphate (Pi), creatine phosphate (CP) and ATP). During perfusion, SHR hearts demonstrated higher coronary resistance but no significant differences in LVP or dP/dt. Spontaneously hypertensive rat hearts had lower CP, ATP and CP/Pi ratio and showed a faster fall in cardiac function during anoxia, associated with parallel rates of changes in the phosphate moieties.