Production of acyl-carnitines from the metabolism of [U-14C]3-methyl-2-oxopentanoate by rat liver and skeletal
muscle mitochondria
A.K.M. Jalaluddin Bhuiyan
David Seccombe
Kim Bartlett
Departments of Child Health and Clinical
Biochemistry, The Medical School, University of
Newcastle Upon Tyne, U.K., and Division of
Clinical Chemistry, Department of Pathology,
Vancouver Hospital and University of British
Columbia, Vancouver, British Columbia, Canada
(Original manuscript submitted 25/1/94; received in revised form
27/10/94; accepted 1/11/94)
Copyright 1996 Canadian Medical Association
Abstract
A sensitive method of continuous on-line radio high performance liquid
chromatography (HPLC) was used to detect the specific radio-labelled
acyl-carnitine esters derived from the oxidation of
[U-14C]3-methyl-2-oxopentanoate by rat liver and muscle
mitochondrial fractions.
The recoveries of carnitine, acetyl-carnitine, propionyl-carnitine,
2-methylbutyryl-carnitine, and hexanoyl-carnitine were 98.7% (± 5.4;
SEM, n = 3), 91.4% (± 7.6), 89.4% (± 5.2), 84.6%
(± 6.8), and 87.9% (± 7.8), respectively, from quenched
mitochondrial incubations. This method demonstrated that rat liver and
muscle mitochondria generate acetyl-carnitine, propionyl-carnitine and
2-methylbutyryl-carnitine when incubated with
[U-14C]3-methyl-2-oxopentanoate in the presence of carnitine.
The production of
acetyl-carnitine was almost similar in the 2 tissues. Muscle mitochondria
produced higher amounts of propionyl-carnitine and 2-methylbutyryl-carnitine than liver mitochondria. These observations suggest a limited
utilisation of propionyl-CoA by muscle mitochondria which, through a
mechanism of feed-back inhibition, may have contributed to the
accumulation of 2-methylbutyryl-CoA. This study provides further evidence
for the importance of carnitine in the modulation of the mitochondrial [acyl-CoA]/[CoA] pool.
Clin Invest Med 1995; 18 (2): 144-151
Table of contents: CIM vol. 18, no. 2