The role of ornithine decarboxylase in enterocyte mitochondrial
function and integrity.
Madsen, K. L., P. D. Brockway, L. R. Johnson, J. A. Hardin, D. G.
Gall.
Division of Gastroenterology, University of Alberta, Edmonton,
Alberta, Gastrointestinal Research Group, Health Sciences Centre,
University of Calgary, Calgary, Alberta and Department of Physiology
and Biophysics, Health Sciences Centre, University of Tennessee,
Memphis, Tennessee
APStracts 2:0229G, 1995.
We examined the role of ornithine decarboxylase and polyamine
biosynthesis in regulating mitochondrial function and integrity along
the crypt-villus axis in male Sprague Dawley rats. Isolated
enterocytes from villus tip region in control rats demonstrated a
greater cellular capacity for glucose oxidation compared with crypt
regions as evidenced by increased CO2 production from [14C]glucose
and 2-[14C]pyruvate in association with elevated lactate and
intracellular ATP. Activity of the mitochondrial enzymes NADH
dehydrogenase [EC 1.6.99.3], succinic dehydrogenase [EC 1.3.99.1],
and cytochrome oxidase [EC 1.9.3.1] were similar along the crypt
-villus axis. To assess the role of ornithine decarboxylase,
enterocytes from control rats were compared with enterocytes isolated
from rats receiving the irreversible ornithine decarboxylase (ODC)
inhibitor [alpha]-diflouromethylornithine (DFMO) for 24 h. Additional
experimental animals received oral spermine (2 [mu]M) at 24 and 16 h
before sacrifice. DFMO treatment did not affect cellular putrescine
or spermine levels, but did result in an increased level of
spermidine in villus and mixed cell populations. Animals receiving
DFMO demonstrated a decreased CO2 production from 2-[14C]pyruvate
along the entire crypt-villus axis coupled with an increase in
lactate production in the upper cell populations. CO2 production from
[14C]glucose and total ATP levels were not affected by DFMO
treatment. Electron microscopy examination showed that mitochondria
in enterocytes corresponding to the population of cells newly emerged
from the crypt during the period of DFMO treatment demonstrated
swelling and bursting due to disruption of the matrix, cristae, and
inner and outer membranes. Mitochondria in crypt and villus tip
enterocytes appeared normal. In DFMO treated animals 2 _M spermine
completely prevented the structural mitochondrial injury as well as
restoring the metabolic crypt-villus gradient. These results suggest
that as enterocytes migrate from the crypt up the villus
mitochondrial function increases in order to handle the increased
metabolic demands placed on the cell by nutrient absorption. ODC
activity and polyamines are necessary for this increased
mitochondrial function as well as having a role in the maintenance of
mitochondrial integrity in maturing enterocytes migrating from the
crypt onto the villus.
Received 25 October 1994; accepted in final form 30 October 1995.
APS Manuscript Number G430-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95