Gut mucosal protein synthesis measured using intravenous and
intragastric delivery of stable tracer amino acids.
Nakshabendi, Imad M, Walid Obeidat, Robin I Russell, Shaun Downie,
Kenneth Smith, and Michael J Rennie.
Department of Gastroenterology, Royal Infirmary, Glasgow G31 2ER,
Scotland, UK and Department of Anatomy & Physiology, University of
Dundee, Dundee DD1 4HN, Scotland, UK
APStracts 2:0154E, 1995.
We measured the rates of mucosal protein synthesis during the
simultaneous delivery of [1-13C]leucine and [1-13C]valine delivered
either intragastrically (i.g.) or intravenously (i.v.) in order to
investigate any influence of the route of supply of the tracers.
Depending on the route, there were marked differences in the gradient
of labeling between the plasma and intramucosal leucine and valine,
ie for i.v. tracers the ratio was 1.73 +/- 0.16 but for i.g. tracers
it was 0.65 +/- 0.12 (P<0.05). Incorporation of i.v. tracer into
mucosal protein was linear with time, and irrespective of tracer
route, the calculated fractional rates of protein synthesis were
identical when based upon the intracellular labeling of the leucine
or valine tracer, ie with i.v., 2.58 +/- 0.32% h-1, with i.g, 2.45
+/- 0.36% h-1. The results demonstrate that a robust and reproducible
method of measurement of gastrointestinal mucosal protein synthesis
has been developed and that use of either i.g. or i.v. routes of
tracer administration gives comparable results. The high rates
measured suggest that the gastrointestinal mucosa contributes
substantially to whole body protein synthesis in normal healthy
subjects.
Received 11 May 1995; accepted in final form 10 July 1995.
APS Manuscript Number E214-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.