The relationship between cytotoxicity induced by N-
nitrosofenfluramine and mitochondrial or glycolytic
adenosine triphosphate (
ATP) synthesis-dependent intracellular bioenergetics was studied in isolated rat hepatocytes. The supplementation of
fructose, an
ATP-generating glycolytic substrate, to hepatocyte
suspensions prevented N-
nitrosofenfluramine-induced cell injury accompanied by the formation of cell
blebs, abrupt loss of intracellular
ATP and
reduced glutathione and mitochondrial membrane potential (DeltaPsi), and the accumulation of
oxidized glutathione and
malondialdehyde, indicating lipid peroxidation, during a 2h incubation period.
Fructose (1-20mM) resulted in concentration-dependent protection against the cytotoxicity of N-
nitrosofenfluramine at a concentration of 0.6mM, a low toxic dose. Pretreatment with
xylitol, another glycolytic substrate, at concentration of 15mM also prevented the cytotoxicity caused by the nitroso compound, but neither
glucose nor
sucrose exhibited protective effects. In addition,
fructose inhibited N-
nitrosofenfluramine (0.5 and 0.6mM)-induced DNA damage, as evaluated in the comet assay, indicating that nuclei as well as mitochondria are target sites of the compound. These results indicate that (a) the onset of N-
nitrosofenfluramine-induced cytotoxicity in rat hepatocytes is linked to mitochondrial failure, and that (b) the insufficient supply of
ATP in turn limits the activities of all energy-requiring reactions and consequently leads to acute cell death.