The contribution of impaired degradative processes to the cellular cha
nges occurring in the brain as a consequence of chronic ethanol exposu
re was assessed. Male Wistar rats were fed nutritionally adequate liqu
id diets containing ethanol as 35% of total dietary calories. Controls
were pair-fed identical amounts of the same diet in which ethanol was
replaced by isocaloric glucose. The results showed that at the end of
3 weeks the activities of neutral protease (nonlysosomal) and catheps
in D (lysosomal) were unaltered. However, there were significant eleva
tions in the activities of the lysosomal enzyme cathepsin B, regardles
s of whether the activities were expressed relative to wet weight (p =
0.005), protein (p = 0.006), or DNA (p = 0.045). In addition, we show
ed that the activities of cathepsin B were not significantly affected
by additions of carnosine or acetaldehyde, in vitro. However, neutral
protease activities were increased by carnosine additions in vitro. We
conclude that selective alterations in brain protease activities may
be contributing factors in the genesis of alcoholic brain disorders.