Circadian rhythm and dietary response of disaccharidase activities in isolated rat jejunum.

Studies were made on the effects of intraluminal factors on the circadian rhythm and the adaptive change to diet of maltase and sucrase activities in rat small intestine. Rats given carbohydrate-free diet for 1 week showed lower specific activities of these enzymes than rats on the latter diet. Segments of jejunum, isolated as blind sacs with normal blood and nerve supplies, showed the same circadian rhythm as unligatured jejunum, but their enzyme activities were not increased by administration of carbohydrate-rich diet for 1 week. Thus it was concluded that the adaptive changes of disaccharidase activities caused by change in diet depend primarily on the presence of carbohydrate in the intestinal lumen, whereas the circadian rhythmic changes do not.