PROTON-RESONANCE SPECTROSCOPY STUDY OF THE EFFECTS OF L-ORNITHINE-L-ASPARTATE ON THE DEVELOPMENT OF ENCEPHALOPATHY, USING LOCALIZATION PULSES WITH REDUCED SPECIFIC ABSORPTION RATE

Using the SADLOVE (single-shot adiabatic localized volume excitation) localization technique with reduced specific absorption rate phase-compensated 2 pi pulses for localization, in vivo rat brain spectra were obtained in order to study the possible beneficial effects of L-ornithine-L-aspartate (OA) on the development of encephalopathy induced by hyperammonemia in por tacaval shunted rats, an experimental model for subacute hepatic encephalopathy. The in vivo H-1 spectra were quantified using a conjugate-gradient-based frequency-domain fitting procedure. OA treatment resulted in an about threefold lower increase in train lactate (P < 0.0001) and a slower increase of brain glutamine (P = 0.022) concentration. However, these changes in brain metabolism, including a significantly lower ammonia concentration during OA treatment, were not associated with a sig significant improvement in clinical symptoms of encephalopathy, suggesting either insufficient decrease in brain ammonia concentration or another effect of OA treatment counteracting the lowering effect on blood and brain ammonia and on brain glutamine and lactate. It is concluded that localized in vivo H-1 MRS of the brain in combination with other analytical techniques, such as in vine microdialysis, is helpful in explaining pathophysiological changes during hyperammonemia-induced encephalopathy. (C) 1994 Academic Press, Inc.