Inconsistent Effect of
Nitric Oxide on Lipolysis in Isolated Rat Adipocytes
N. CANOVÁ, D. LINCOVÁ, H. FARGHALI
Institute of Pharmacology, First Faculty of Medicine, Charles
University, Prague, Czech Republic
Received August 13, 2004
Accepted October 19, 2004
On-line available December 9, 2004
Summary
Though two isoforms of nitric oxide synthase, iNOS and eNOS,
were reported in adipocytes, the role of NO in adipose tissue is
still ambiguous. The aims of the present study were 1) to follow
the effect of bacterial lipopolysaccharide (LPS), on 24
h-lipolysis in rat epididymal adipocyte culture in relation to
iNOS stimulation; 2) to compare LPS-induced NO effects with
exogenously NO, delivered as S-nitroso-N-acetylpenicillamine
(SNAP), and 3) to examine the possible role of NO signaling
agonist in lipolysis mediated by the -adrenoreceptor agonist.
Lipolysis was measured by glycerol and free fatty acid (FFA)
production. The medium nitrite levels were used for the indirect
estimation of NOS expression. Adipocyte mitochondrial function
was assessed by the MTT test. LPS produced a
concentration-dependent increase of NO with a decrease of
viability at the highest dose. However, LPS did not affect
lipolysis. SNAP did not exhibit significant changes in glycerol,
FFA or MTT. BRL-37344 and db-cAMP significantly increased
nitrite, glycerol and FFA levels. There was a positive
correlation between glycerol release and nitrite production.
Moreover,
BRL-37344 significantly reduced mitochondrial functions. The
pretreatment with bupranolol, -antagonist, restored all
parameters affected by BRL-37344. These results support a
concept that NO fulfils multifaceted role of stimulating
lipolysis under physiological conditions (-agonistic effect)
and modulating the same processes during inflammatory (LPS)
processes.
Key words
Rat adipocytes • Nitric oxide • Lipopolysaccharide •
Beta-adrenoreceptor • Lipolysis
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