N-acetylcysteine improves cytotoxic activity of cirrhotic rat liver-associated mononuclear cells.

Liver cirrhosis, which is associated with decreased plasma and hepatic glutathione (GSH), has been reported to cause the suppression of NK activity in peripheral blood mononuclear cells. Since low GSH levels in lymphocytes are known to alter lymphocyte function, we examined the correlation between intracellular GSH levels and the cytotoxic activity of liver-associated mononuclear cells (liver MNC). We show here that rat liver contains a highly active population of NK cells (CD3- NKR-P1 + cells) that kill Yac-1 in vitro and that the cytotoxic activity of this NK population is directly proportional to liver MNC GSH. This proportionality is independent of the methods used to alter GSH level. Thus, in vitro treatment of liver MNC with buthionine sulfoximine to lower GSH levels lowers the cytotoxic activity. MNC from cirrhotic liver, in which implanted tumor cells grow faster, have both low GSH levels and low cytotoxicity, and supplementation of cirrhotic liver MNC with N-acetylcysteine raises GSH levels and increases cytotoxicity. These findings suggest a physiologic mechanism, i.e. decreased GSH, may be causally associated with the increased incidence of hepatoma in cirrhotic individuals and the increased growth of hepatoma cells in cirrhotic animals. Thus, we suggest that the GSH is important to the optimal functioning of the hepatic immunity that protects against hepatoma development.

Rate of ATP synthesis in the perfused rat liver by 31P cryo-NMR.

ATP concentrations in the perfused rat liver during normoxic perfusion, transient ischemia, and recovery from transient ischemia were measured using the modified 31P cryo-NMR method (Chance, B., Nakase, Y., Bond, M., Leigh, J. S., Jr., and McDonald, G. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4925-4929). Transient ischemia was induced in the perfused livers of starved rats, and multiple freeze-trapped tissue samples were taken from each liver at short intervals (15-30 s) during ischemia or following reperfusion. The freeze-trapped tissue was pulverized together with an antifreezing agent and high energy metabolites were measured by 31P NMR at 243 K after thawing. By using the cryo-NMR technique, a biochemical time resolution of 2 s could be achieved. Absolute metabolite concentrations were calculated by comparing the peak areas with internal standards mixed into the samples. Good time resolution and reliable concentration measurements provided by the cryo-NMR method enable us to estimate the ATP synthesis rate in the perfused liver during reperfusion following transient ischemia. The rate of ATP synthesis in the normoxic perfusion was 1.95 mumol/min/g wet weight; the maximal ATP synthesis rate during the recovery phase from ischemia was 5.75 mumol/min/g wet weight.