Methionine enkephalin accumulates in plasma but not in brain or cerebrospinal fluid of rats with acute toxic hepatitis.

In order to determine whether acute toxic hepatitis in the rat is associated with an accumulation of methionine enkephalin in plasma and increased blood-to-brain transfer of methionine enkephalin, immunoreactive methionine enkephalin levels were determined by radioimmunoassay in plasma, cerebrospinal fluid and whole brain samples from rats with thioacetamide induced acute toxic hepatitis. Thioacetamide treatment was associated with an 8.7-fold increase in plasma immunoreactive methionine enkephalin levels (P less than or equal to 0.005) 24 h after treatment. However, this marked elevation in plasma immunoreactive methionine enkephalin levels was not associated with an increase in whole brain or cerebrospinal fluid immunoreactive methionine enkephalin levels. These data suggest that increased plasma-to-brain transfer of methionine enkephalin does not occur in this model of acute toxic hepatitis.