Circadian rhythmicity in several small intestinal functions is independent of use of the intestine

Abstract

Fifty ml of a liquid diet were administered daily to rats in 3 different ways: orally, beginning at 0000 h; by continuous i.v. infusion; and by discontinuous i.v. infusion from 0000 to 1400 h. Animals were killed every 6 h over a 24 h period. Activity profiles as a function of time of day were determined for the following small intestinal parameters; monosaccharide transport; 5 disaccharidases; alkaline phosphtase; .gamma.-glutamyltransferase; leucylnaphthylamide hydrolyzing activity; villus height and width and number of columnar cells lining a villus section. Circadian rhythmicity as previously reported was observed for all parameters in rats fed orally for 7 days but was not observed in any parameters in rats fed by continuous infusion for 9 days. Rats fed by discontinuous infusion for 10 days maintained carcadian rhythmicity in the following functions: monosaccharide transport; disaccharidase activities and columnar cell number. Rhythmicity in these functions can exist without nutrient delivery to the alimentary tract and presumably arises from involvement of a neuro-endocrine component. The other activities tested appear to require the alimentary tract for the existence of circadian rhythmicity.