Journal zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Hepatology 2000; 33: 216223 Printed in Denmark All rights wserved Munksgaard Copenhagen ., zyxwvutsrqponm Journal of Hepatology ISSN 0168-8278 Relationship between hepatic mitochondrial functions in vivu and in vitro in rats with carbon tetrachloride-induced liver cirrhosis Lukas Krahenbiihl’, Monika Ledermann2, Corinne Lang2 and Stephan Krahenbtih12 Depurtments zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of 1 Visceral and Trunsplantation Surgery and 2Clinical Pharmacology, University qf Berne, Switxrland Background/Aims: The metabolic capacity of liver mitochondria is impaired in rats with carbon tetra- chloride (CCL&-induced cirrhosis. These studies were performed to find out whether benzoate and/or palmi- tate are suitable substrates for assessing hepatic mito- chondrial function in vivo. Methods: In vivo metabolism of benzoate and 1-14C- pahnitate was assessed by monitoring urinary ex- cretion of hippurate and exhalation of 14COz, respec- tively, in cirrhotic and control rats (n=8 for each group). Isolation of liver mitochondria, and in vitro benzoate and palmitate metabolism were performed by methods published previously. The hepatic content of mitochondria was assessed by stereological analysis of the volume of hepatocytes and by biochemical de- termination, using the activity of citrate synthase. Results: Renal excretion of hippurate following i.p. administration of benzoate was reduced in cirrhotic rats (64215 vs. 85+14% of administered dose over 24 h), and showed a linear correlation with hippurate formation by isolated mitochondria. The activities of benzoyl-CoA synthase and benzoyl-CoA:glycine N- acyltransferase were reduced by approximately 60%, and the coenzyme A content by 50% in hepatic mito- chondria from cirrhotic rats, explaining impaired hip- p” VIOUS STUDIES have shown that the metabolism of benzoate reflects the function of hepatic mito- chondria in both patients (1,2) and rats with chronic liver disease (3,4). In rats with long-term cholestasis, an animal model for secondary biliary cirrhosis (5) the formation of hippurate from benzoate was found to be increased in vivo but decreased in vitro by isolated Received 28 August; revised I7 December 1999; accepted 13 January 2000 Correspondence: Stephan Krghenbiihl, Clinical Pharma- cology, University Hospital, CH-403 1 Basel, Switzerland. Tel: 41 61 265 47 15. Fax: 41 61 265 45 60. e-mail: kraehenbuehl@uhbs.ch purate formation. Peak exhalation of r4C02 after i.p. administration of 1-r4C-palmitate was reduced by 44O/ and the area under the 14C02 exhalation-time curve by 34% in cirrhotic rats. Peak r4C02 exhalation revealed a linear correlation with oxidative met- abolism of palmitoylcarnitine in isolated mitochon- dria. Both in vivo benzoate and pahnitate metabolism showed a linear correlation with the volume fraction of hepatocytes. The mitochondrial protein content was reduced in cirrhotic rats per g liver and per liver but equal to control rats per volume of hepatocytes. Conclusions: In vivo metabolism of both palmitate and benzoate reflects hepatic mitochondrial function in rats with CCkinduced cirrhosis. Hepatic mito- chondrial function is impaired in rats with CCL-in- duced cirrhosis due to both reduced mitochondrial volume per liver and impaired metabolism of the re- maining mitochondria. In contrast to rats with sec- ondary biliary cirrhosis, rats with CCL,-induced cir- rhosis showed no hepatic mitochondrial proliferation to counteract reduced mitochondrial function. Key words: Benzoate metabolism; Mitochondrial pro- liferation; Palmitate metabolism; Respiratory chain. mitochondria, findings which were explained by pro- liferation of hepatic mitochondria with impaired func- tion (6). In rats with carbon tetrachloride (CCL&in- duced liver cirrhosis the function of the respiratory chain of hepatic mitochondria was also impaired (7- 9). However, in contrast to rats with secondary biliary cirrhosis (10,l l), stereological studies in rats with CCld-induced cirrhosis have shown no proliferation of hepatic mitochondria (12). Rats with CC&-induced cir- rhosis maintain the content of hepatic mitochondria when expressed per hepatocyte but have a reduced mitochondrial content per whole liver (12). These find- ings are explained mainly by “loss of hepatocytes”, 216