Parallel between circadian rhythms of intestinal disaccharidases and foot intake of rats under constant lighting conditions.

The relationship between the circadian rhythmic changes in the disaccharidase activities of the small intestine and the circadian feeding pattern was investigated in rats kept in the dark or in the light continuously for 4 weeks. Rats kept continuously in the light and fed ad libitum showed no rhythmic change in food intake or disaccharidase activities, but when they were only fed during a restricted time of day, their disaccharidase activities showed rhythmic changes with higher activities around the feeding time. In contrast, rats kept continuously in the dark and fed ad libitum showed circadian variations in food intake and disaccharidase activities essentially similar to rats kept under the normal light-dark lighting schedule. These findings show that the rhythm of disaccharidase activities is synchronized with the feeding rhythm, not with the lighting rhythm.