Circadian rhythms of four marker enzymes activity of the jejunal villi in man.

Bioptic specimens taken from the lower duodenum were studied in 12 volunteers at different times of the day for the activity of 4 marker enzymes. The activity of alkaline phosphatase in brush border of villi was the strongest at 06h, while the nadir at 22h; acid phosphatase activity in the supranuclear zone and in macrophages was the strongest at 06h and reduced at other test times; the peak activity of 5' nucleotidase was found at 14h with the nadir at 02h; activity of NADPH was the strongest at 18h. It is suggested that circadian rhythmicity of intestinal function exists in man like in animals.