نبذة مختصرة : The objective of this study was to examine the in vivo effect of melatonin on rat mitochondrial liver respiration. Two experiments were performed: For experiment 1, adult male rats received melatonin in the drinking water (16 or 50 mg=ml) & vehicle during 45 days. For experiment 2, rats received melatonin in the drinking water (50 mg=ml) for 45 days, or the same amount for 30 days followed by a 15 day-withdrawal period. At sacrifice, a liver mitochondrial fraction was prepared and oxygen consumption was measured polarographically in the presence of excess concentration of DL-3-b-hydroxybutyrate or L-succinate. Melatonin treatment decreased Krebs’ cycle substrate-induced respiration significantly at both examined doses. The stimulation of mitochondrial respiration caused by excess concentration of substrate recovered after melatonin withdrawal. Basal state 4 respiration was not modified by melatonin. Melatonin, by curtailing overstimulation of cellular respiration caused by excess Krebs’ cycle substrates, can protect the mitochondria from oxidative damage. ; Fil: Reyes Toso, Carlos Felipe. Universidad de Buenos Aires. Facultad de Medicina; Argentina ; Fil: Rebagliati, Ines Rosa. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina ; Fil: Ricci, C. R. Universidad de Buenos Aires. Facultad de Medicina; Argentina ; Fil: Linares, L. M. Universidad de Buenos Aires. Facultad de Medicina; Argentina ; Fil: Albornoz, L. E. Universidad de Buenos Aires. Facultad de Medicina; Argentina ; Fil: Cardinali, Daniel Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Medicina; Argentina ; Fil: Zaninovich, A. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
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