Partial hepatectomy with or without endotoxin does not promote apoptosis in the rat liver

Liver insufficiency and failure has been described following subtotal hepatectomy. The cause is poorly understood but may be because of attrition of hepatocytes through enhanced cell death pathways such as apoptosis. The trigger for this could be reduction beyond a critical mass of liver tissue or the influence of endotoxin (LPS) on cytokine activation. The experiment was designed to answer these questions.

Rats were subjected to either 30% or 70% hepatectomy. Sacrifice occurred on either postoperative day 2 or 4. At sacrifice remnant livers were examined for apoptosis through the direct Tunel immunoperoxidase method (apoptotic index) and soluble histone ELISA. A second group of rats underwent 30% or 70% hepatectomy and were given either saline or endotoxin (LPS). Sacrifice occurred on postoperative day 1, 2, or 4. Liver samples were analyzed for apoptosis by Tunel immunoperoxidase, histone-associated DNA, TNF-alpha, and caspase-3. Mitotic activity and evidence of hepatocellular necrosis were also determined.

By comparison to prehepatectomy values, rats subjected to hepatectomy alone failed to disclose any effect of resection on apoptotic activity. By comparison to sham operated controls there was a modest but significant increase in apoptotic activity at day 4 in the 30% and 70% hepatectomized rates by apoptotic index but not the soluble histone ELISA. Injection of LPS without hepatectomy produced an increase in apoptotic activity by apoptotic index and soluble histone ELISA methods on day 1 and 2. The addition of 30% or 70% hepatectomy produced a sporadic, but not sustained, increase in apoptotic activity which may have been because of LPS injection alone. Tissue TNF-alpha levels increased with LPS but changed little with addition of hepatectomy. Mitotic activity remained essentially unchanged with or without LPS injection. No evidence of hepatocellular necrosis was detected with LPS and extended hepatectomy.

Apoptosis does not appear to be a prominent feature in the posthepatectomy liver, with or without addition of LPS. Even with accelerated TNF-alpha production from LPS, the mitotic pathways continue to take precedent. Apoptosis, except for occasional sporadic bursts, is effectively suppressed. It is not likely that apoptosis contributes to depletion of functional hepatocytes and liver insufficiency.