The circadian rhythm of intra-acinar profiles of alcohol dehydrogenase activity in rat liver: a microquantitative study.

Using microquantitative measurements of alcohol dehydrogenase activity in microdissected samples of liver tissue along the sinusoidal length, the intra-acinar distribution profiles were studied in seven groups of female rats at different times during 24 h with a light phase from 6:30 h to 18:30 h. The mean values of alcohol dehydrogenase activity showed a circadian rhythm with a minimum at 13.30 h and a maximum at 17.30 h (p less than 0.001). However, the intra-acinar gradients remained almost unchanged, indicating that increase and decrease in enzyme activity takes place simultaneously in all parts of the liver acinus. This observation, together with data from the literature, suggests that the circadian rhythm of alcohol dehydrogenase activity reflects variations in different liver cell constituents, rather than enzyme protein synthesis or proteolysis.