Effect of physical activity and fasting on gut and liver
proteolysis in the dog.
Halseth, Amy E., Paul J. Flakoll, Erica K. Reed, Allison B. Messina,
Mahesh G. Krishna, D. Brooks Lacy, Phillip E. Williams, and David H.
Wasserman.
Department of Molecular Physiology and Biophysics, Diabetes
Research and Training Center and Department of Surgery, Vanderbilt
University School of Medicine, Nashville, TN 37232
APStracts 4:0187E, 1997.
The aim of this study was to determine how gut and liver protein
kinetics adapt to acute exercise in the 18 h fasted dog (n=7) and in
dogs glycogen-depleted by a 42 h fast (n=8). For this purpose,
sampling (artery and portal vein, hepatic vein) and infusion (vena
cava) catheters and Doppler flow probes (portal vein, hepatic artery)
were implanted under general anesthesia. At least 16 days later, an
experiment, consisting of a 120 min equilibration period, a 30 min
basal sampling period, and a 150 min exercise period, was performed.
At the start of the equilibration period, a constant rate infusion of
1-13C-leucine was initiated. Gut and liver leucine appearance and
disappearance rates were calculated in these studies by combining a
novel stable isotopic method and arteriovenous difference methods. In
the determination of tissue leucine kinetics the tissue inflow of
both 13C-[alpha]- ketoisocaproic acid (KIC) and 13C-leucine were
taken into account. The results of this study show that (1) the
splanchnic bed (liver plus gut) contributes 40% to the whole body
proteolytic rate in the basal state and during exercise in dogs
fasted for either 18 or 42 h; (2) the contributions of the gut and
liver to splanchnic bed proteolysis is about equal in the basal state
in both 18 and 42 h fasted dogs; and (3) exercise in the 18 h fasted
dog leads to a greater emphasis on gut proteolysis and a lesser
emphasis on hepatic proteolysis. These studies highlight the
important contribution of gut and hepatic proteolysis to whole body
proteolysis, and the ability of the gut to acutely adapt to changes
in physical activity.
Received 19 February 1997; accepted in final form 8 August 1997.
APS Manuscript Number E80-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 27 August 1997