Circadian coupling between pancreatic secretion and intestinal motility inhumans

Human interdigestive intestinal motility follows a circadian rhythm with re duced nocturnal activity, but circadian pancreatic exocrine secretion is un known. To determine whether circadian changes in interdigestive pancreatic secretion occur and are associated with motor events, pancreatic enzyme out puts, proximal jejunal motility, and plasma pancreatic polypeptide concentr ations were measured during consecutive daytime and nighttime periods (12 h each) in seven healthy volunteers using orojejunal multilumen intubation. Studies were randomly started in the morning or evening. Nocturnally, motil ity decreased (motor quiescence: 67 +/- 22 vs. 146 +/- 37 min; motility ind ex: 3.59 +/- 0.33 vs. 2.78 +/- 0.40 mmHg/min; both P < 0.05) but amylase ou tput increased (273 +/- 78 vs. 384 +/- 100 U/min; P < 0.05) and protease ou tput remained unchanged (P > 0.05); consequently, enzyme/motility ratio inc reased. Amylase outputs were always lowest during phase I. Motor but not pa ncreatic circadian activities were associated with sleep. Pancreatic polype ptide plasma concentrations were unchanged. Consequently, intestinal motor and pancreatic exocrine functions may have different circadian rhythms, i.e ., decreased motor and stable secretory activity during the night. However, the association between individual phases of interdigestive motor and secr etory activity is preserved. The nocturnal increase in enzyme/motility rati o is probably not caused by increased cholinergic tone.