As nitric oxide is considered a mediator of liver oxid ative metabolism during sepsis, we studied the effects of exogenous nitric oxide, produced by NO-donor, (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), on cell viability, urea biosynthesis and oxygen consumption in rat hepatocyte cultures. Nitric oxide release from NOR-3 was studied using 4,5-diaminofluorescein diacetate. Urea levels were measured by the spectrophotometric method. Cell viability was determined by the MTT test and trypan blue exclusion test, whereas oxygen consumption was measured by a polarographic technique. After 2 h treatment, NOR-3 induced an increase in the levels of nitric oxide. After 2 h of treatment and 24 h after the end of the treatment with NOR-3, both cell viability and urea synthesis were significantly reduced in comparison to the controls for NOR-3 concentrations equal to or greater than 50 μM. A reduction in oxygen consumption was observed in hepatocytes after 40 min treatment with 100 μM NOR-3, even if the cell viability was unchanged. Reduction of oxygen consumption is an early indicator of the metabolic alterations in hepatocytes exposed to nitric oxide. These findings suggest that nitric oxide accumulation acts on hepatocyte cultures inducing cell death and reduction of urea synthesis after 2 hours., R. Chimenti, G. Martino, S. Mazzulla, S. Sesti., and Obsahuje bibliografii a bibliografické odkazy
Glucagon and α-adrenergic-induced glycog enolysis is realized via the agonist/adenylyl cyclase/cAMP/protein kinase signaling pathway or via the activation of phosphorylase kinase by the mobilized calcium that supports the inhibition of glycogen synthase, respectively. The role of nitric oxide (NO) in this process has not been extensively studied. The present work was directed to the question whether NO is produced during glucagon-induced glycogenolysis in rat hepatocyte in a similar way like α-adrenoceptor stimulation. Glycogen-rich hepatocyte cultures were used. NO production (NO2-) was assessed under the influence of glucagon, dibutyryl cyclic AMP (db-cAMP), forskolin, the nitric oxide synthase (NOS) inhibitors Nω-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, and the NO donor S-nitroso-N-acetyl penicillamine (SNAP). Inducible NOS (iNOS) mRNA was examined by reverse transcription-polymerase chain reaction. Glycogenolysis was followed up by estimation of medium glucose levels. The amount of glucose and NO2- released by glycogen-rich hepatocytes was increased as a result of glucagon, db-cAMP, forskolin and SNAP treatments. iNOS gene expression was upregulated by glucagon. Glycogenolysis that occurs through glucagon receptor stimulation involves NO production downstream of transduction pathways through an isoform of NO synthase. The present and previous studies document possible involvement of NO signaling in glycogenolytic response to glucagon and adrenergic agonists in hepatocytes., H. Farghali, J. Hodis, N. Kutinová-Canová, P. Potměšil, E. Kmoníčková, Z. Zídek., and Obsahuje bibliografii a bibliografické odkazy