TUMOR-NECROSIS-FACTOR-ALPHA DIFFERENTIALLY MODULATES THE CELLULAR-RESPONSE OF RAT HEPATOCYTES IN PERIPORTAL-EQUIVALENT AND PERICENTRAL-EQUIVALENT CULTURES

Alterations of cellular functions induced by recombinant human tumor n ecrosis factor cu (TNF alpha) were compared in rat hepatocytes culture d under either periportal-equivalent (10 nM insulin; 10 nM glucagon; 1 3% O-2) or perivenous-equivalent conditions (10 nM insulin; 1 nM gluca gon; 4% O-2), TNF alpha induced a time- and dose-dependent increase in nitric oxide (NO) production and an acute phase response (inhibition of albumin secretion and elevation of alpha(2)-macroglobulin productio n) under both culture conditions. NO production was more pronounced in periportal cultures, while the acute phase response was stronger in p ericentral cultures. This suggests that NO production and the acute ph ase response are controlled by different pathways. After exposure to T NF alpha, DNA content was measured fluorimetrically and biochemically. A marked decrease in nuclear DNA content was found exclusively in per icentral cultures after an 8-h exposure, followed by an elevation of l actic dehydrogenase (LDH) release after a 12-h exposure. Aurintricarbo xylic acid (100 mu M), an inhibitor of endonuclease, significantly inh ibited the TNF alpha-induced decrease in nuclear DNA content but only partially inhibited the LDH release. This indicates that the loss of n uclear DNA content in pericentral cultures is due to an activation of endonuclease and the resulting DNA fragmentation and does not correlat e with NO production. Furthermore, the release of LDH seems to be only partially associated with DNA damage. Dexamethasone (100 nM) complete ly inhibited both TNF alpha-induced DNA fragmentation and the elevatio n of LDH release. The results clearly indicate that the toxicity of TN F alpha is influenced by the metabolic state of hepatocytes. According ly, the preferential perivenous cell injury observed after exposure to endotoxins in vivo seems to be due to a higher sensitivity of the per icentrally localized hepatocytes towards TNF alpha rather than a TNF a lpha concentration gradient.