INVESTIGADORES
PODEROSO Juan Jose
congresos y reuniones científicas
Título:
DT-diaphorase activity from septic rat lung and its modification by peroxynitrite
Autor/es:
SCHÖPFER F; FINOCCHIETTO P; PERALTA JG; BOVERIS A; PODEROSO JJ
Lugar:
Florianópolis, Brasil
Reunión:
Congreso; First Meeting of the South American Group for Free Radical Research; 1999
Institución organizadora:
South American Group for Free Radical Research
Resumen:
The quinone reductase, DT-diaphorase (DTD) catalizes, in a direct two-electron transfer reaction, the reduction of membrane-bound ubiquinone (UQ) to ubiquinol (UQH2). This activity regenates UQ antioxidant capacity, thereby providing protection to damage from free radical increase, produced in different pathopphysiological conditions. During sepsis different enzymatic catalized reactions increase nitrogen and oxygen free radicals, which lead to the formation of oxidants like peroxynitrite and hydrogen peroxide. The aim of the present work was to study DTD activity as a protective mechanism against oxidants in lung during sepsis after fecal peritonitis. In Sprague-Dawley rats (220-250 g) (n=8) sepsis was induced by cecal ligation and double punction (2CLP) and tissue samples from lung were obtained at 4 and 16 h from 2CLP in septic, control and sham operated rats. Tissues were homogeneized and  centrifugated at 8000 g and DTD activity was assessed by dicumarol-sensitive DCPIP reduction using NADFPH as substrate; results are expressed in nmoles reduced DCPIP/min/mg protein. DTD activity was significantly increased (p<0.05) in 4 h 2CLP animals in all studied tissues in comparison to control and sham operated animals: lung (92.06±6.88 vs 330.52±54.46) Interestingly, DTD activities measured in lung samples of 16 h septic rats showed a decrease (p<0.05) respect to sham samples and 4 h septic rats: (155.67±24.39 vs 330.52±54.46). In order to evaluate if this decrease can be ascribed to inactivation of DTD activity by ONOO-, we analized the effects of ONOO- single pulses (50-400 mM) on DTD activity of supernatants. DTD activity was effectively inhibited by ONOO- with an IC50 of 150 mM in supernatants of control and septic rats. Finally, we conclude that DT diaphorase activity increases during early sepsis could represent a new mechanism of protection particularly in the lung. But also, it coul be affected during sepsis evolution by peroxynitrite and thus decreases the antioxidant capacity of the organ, leading to enzyme inhibition and contributing to lipoperoxidation and final organ failure.