Circadian rhythms of biliary protein and lipid excretion in rats

A. Nakano, P. S. Tietz, Nicholas F La Russo

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

To gain insight into the mechanisms by which hepatocytes release lipids and proteins into bile, we studied extended, steady-state secretion of bile, lipids, and lysosomal and canalicular membrane proteins in freely moving, unanesthetized rats with chronic bile fistulas. We found circadian rhythms of biliary secretion for all measured constituents. In the basal state (nocturnal feeding), two distinct secretory patterns emerged: type 1, characterized by a peak at midnight and a nadir at noon; and type 2, characterized by a peak at 8 A.M. and a nadir at 8 P.M. We observed parallel, type 1 circadian rhythms of excretion for bile, biliary lipids (bile acid, cholesterol, phospholipid), and a canalicular membrane enzyme (alkaline phosphodiesterase I). In contrast, a type 2 circadian rhythm was observed for the outputs of two lysosomal enzymes. Hepatic lysosomal enzyme concentrations and the number of pericanalicular lysosomes decreased (P < 0.05) by 15 and 35%, respectively, at the nadir of their biliary output relative to the time of their peak outputs. In response to daytime feeding, major shifts in the circadian rhythms of excretion of biliary constituents occurred such that secretion of bile, lipids, and the canalicular membrane protein adopted a type 2-like rhythm, whereas the biliary secretion of the lysosomal proteins exhibited a type 1-like pattern. These results indicate that bile flow and biliary excretion of individual lipids and proteins exhibit distinct circadian rhythms that are altered by feeding. Secretory events at the canaliculus that depend on the transmembrane flux of bile acids, such as water and lipid movement or the solubilization of membrane proteins, display a common rhythm. In contrast, secretory processes independent of bile acid flux, such as the exocytic discharge of lysosomal protein, display a different rhythm.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume258
Issue number5 21-5
StatePublished - 1990

Fingerprint

Circadian Rhythm
Bile
Lipids
Bile Acids and Salts
Proteins
Membrane Proteins
Enzymes
Lysosome-Associated Membrane Glycoproteins
Phosphodiesterase I
Water Movements
Secretory Pathway
Lysosomes
Fistula
Hepatocytes
Phospholipids
Cholesterol
Membranes
Liver
Hepatobiliary Elimination

Keywords

  • biliary excretion
  • exocytosis
  • lysosome

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

Cite this

Circadian rhythms of biliary protein and lipid excretion in rats. / Nakano, A.; Tietz, P. S.; La Russo, Nicholas F.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 258, No. 5 21-5, 1990.

Research output: Contribution to journalArticle

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