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