Energy linked uptake of demethylphalloin by isolated rat liver cells

Isolated hepatocytes accumulate demethylphalloin (DMP) under aerobic conditions. In the absence of oxygen the initial rate of the DMP uptake is reduced to less than 20%, while reoxygenation restores the transport. Liver cells release previously accumulated phallotoxin when the oxygen supply is interrupted. DMP uptake is blocked by oligomycin, antimycin A, carbonylcyano-chlorophenylhydrazon (CCCP) or dinitrophenol and is partially inhibited by carboxyatractyloside. Depletion of ATP in hepatocytes by replacement of glucose by fructose reduces the accumulation of toxin too. Below 22 degrees C no uptake was measurable. Between 22 degrees and 37 degrees C an apparent activation energy of 76.6 kJ/mol toxin and a Q10 of 2.6 was calculated for the carrier mediated uptake of DMP. The results suggest that the uptake of demethylphalloin is an energy dependent substrate transfer very similar to that of cholate.