Hepatic passage of bile acids increases oxygen uptake by perfused rat liver

The Effects of Local Anesthetics on Bile Flow, Potassium Equilibrium and Oxygen Consumption in the Perfused Rat Liver

Amide local anesthetics mainly undergo hepatic metabolism. Specific applications, such as catheter application for long-term pain therapy, may result in large plasma concentrations. As it is unknown whether local anesthetics influence liver function, we examined the influence of lidocaine, bupivacaine, and ropivacaine in concentrations of 1 and 10 microg/mL on the metabolic activity of the perfused rat liver. At the large concentrations, all three local anesthetics caused an immediate increase of oxygen consumption. Bupivacaine and ropivacaine also transiently reduced potassium release. All drugs increased bile flow; this choleretic effect was also significant for bupivacaine and lidocaine in smaller concentrations. In the smaller concentration, only lidocaine significantly increased oxygen consumption. No significant changes in hepatic venous pH were observed. The results show that acute administration of all three local anesthetics results in significant changes of functional variables of the liver. The observed effects appear to result from mitochondrial uncoupling, uptake of the drugs, biliary secretion of their metabolites, and from inhibition of potassium channels. The data provide no evidence that these acute changes may result in enduring postoperative disturbances of liver function, such as cholestasis or jaundice.

Toxicity of bile acids on the electron transport chain of isolated rat liver mitochondria

The toxicity of hydrophilic (cholate) and lipophilic (deoxycholate, chenodeoxycholate, and lithocholate) bile acids on the function of the electron transport chain was investigated in intact and disrupted rat liver mitochondria. In intact mitochondria, lipophilic bile acids used at a concentration of 100 mumol/L (0.1 mumol/mg protein) inhibited state 3 and state 3u (dinitrophenol-uncoupled) oxidation rates for L-glutamate, succinate, duroquinol or ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine as substrates. In contrast, state 4 oxidation rates and ADP/oxygen ratios were not significantly affected. At a bile acid concentration of 10 mumol/L (0.01 mumol/mg protein), the state 3 oxidation rate for L-glutamate was decreased in the presence of deoxycholate, chenodeoxycholate or lithocholate, whereas only lithocholate inhibited state 3 oxidation for succinate or duroquinol. In broken mitochondria, inhibition of oxidative metabolism was found for NADH or duroquinol as substrate in the presence of 100 mumol/L lithocholate (0.2 mumol/mg protein) and for duroquinol in the presence of 100 mumol/L chenodeoxycholate. Direct assessment of the activities of the enzyme complexes of the electron transport chain revealed decreased activities of complex I and complex III in the presence of 100 mumol/L deoxycholate or chenodeoxycholate or 10 mumol/L lithocholate. Inhibition of complex IV required higher bile acid concentrations (300 mumol/L for chenodeoxycholate or 30 mumol/L for lithocholate), and complex II was not affected. Both chenodeoxycholate and lithocholate were incorporated into mitochondrial membranes. The phospholipid content of mitochondrial membranes decreased in incubations containing 100 mumol/L (0.1 mumol/mg protein) chenodeoxycholate but was not affected in the presence of 100 mumol/L lithocholate.(ABSTRACT TRUNCATED AT 250 WORDS)