EFFECTS OF NITROPRUSSIDE AS A NITRIC-OXIDE DONOR ON ANOXIA REOXYGENATION AND D-GALACTOSAMINE HEPATIC INJURIES - A STUDY IN PERFUSED HEPATOCYTES/

At present, the physiological role of NO. synthesis in the liver is am biguous. Studies directed to reveal the role of NO. in relation to liv er function were primarily initiated by an interest in the hepatic res ponse to infections and the consequent modulation of liver function. T he purpose of the present investigation was to use perfused rat hepato cytes to test the ability of the latter to produce NO. and to delineat e the relationship between exogenously delivered NO. and any alteratio n in the degree of injury as produced by anoxia/reoxygenation (AR) or D-galactosamine (GalN, 5 mM) intoxication. NO. production in rats was stimulated by a single dose of lipopolysaccharide (LPS, 20 mg/kg i.p.) from which hepatocytes were isolated and perfused. Exogenous NO. was delivered to the perfusate of hepatocytes that were isolated from untr eated rats, by the addition of sodium nitroprusside (SNP, 2 mM and 0.2 mM). AR and GalN hepatocyte injury was followed after the addition of SNP. Rat hepatocytes were immobilized in low-gelling agarose and perf used with Williams E medium. Endogenous synthesis of NO. and exogenous NO. as produced by SNP was evaluated by estimating the end products o f NO. (NO2-+NO3-) in the perfusion medium. The functional and structur al integrity of hepatocytes was evaluated from lactate dehydrogenase ( LD) leakage and urea synthesis in the perfusion medium. Normal, AR-and GalN-injured hepatocytes did not exhibit measurable NO. while LPS-tre ated hepatocytes produced NO. (80 mu M NO2-+NO3-). SNP-produced NO. si gnificantly increased or decreased LD leakage in AR at 2 mM or 0.2 mM, respectively, and also reduced or increased the rate of urea synthesi s, respectively. 0.2 mM SNP increased trypan blue exclusion by hepatoc ytes. On the other hand, GalN toxicity was not significantly altered b y SNP as demonstrated by LD leakage and the rate of urea synthesis was increased by SNP addition. The present data suggest both deleterious and beneficial role of NO. in AR liver injury model depending on the l evel of NO. generated.