Transglutaminase Activity in Rat Brain after Ethanol Exposure

Abstract

The effect of acute and chronic ethanol treatment on the activity of tissue transglutaminase (a calcium-dependent enzyme that catalyzes the covalent association between proteins, as well as proteins and polyamines) was studied in homogenate and in the cytosolic fraction of rat brain (telencephalon and diencephalon). A single dose of ethanol (5 g/kg of body weight, by gastric intubation) caused a 2-fold increase in enzyme activity at 6 hr after the ethanol dose, with a return toward the basal values at 24 hr. In vitro experiments with ethanol or acetaldehyde showed that the increase in transglutaminase activity was due to ethanol per se and not to its metabolism. The enzyme stimulation was correlated with a decrease in the levels of the polyamine spermine, a physiological substrate for the enzyme. Similar results were also found in the brain from rats fed on an ethanol diet for 4 months. The enhancement in tissue transglutaminase activity may thus lead to a decline in spermine, a polyamine known to have important protective functions in the cell.