Within the framework of our studies on hypertension in various rat strains, we have examined the effect of cyclosporin A (CsA) on intracellular calcium signaling under conditions of oxidative stress. For these preliminary experiments, we have chosen isolated hepatocytes of normotensive rats as a model system for the study of the role of intracellular calcium. We used tert-butyl hydroperoxide (t-BHP, 1 mmol.l-1) as an prooxidant agent. When compared to the controls, we found increased levels of cytosolic free calcium concentration (Ca2+i) during 120 min incubation. The preincubation of hepatocytes with CsA in the concentration of 0.5 m mol.l-1 did not change the physiological level of cytosolic calcium. However, a dual action of CsA on elevated Ca2+i was observed during oxidative injury of hepatocytes: while in the first period of incubation CsA increased Ca2+i, CsA reduced the effect of t-BHP on Ca2+i during the next period of incubation. This indicates the ability of CsA to modify oxidative stress, but further studies are necessary to explain these findings., E. Kmoníčková, L. Kameníková, S. Hynie, H. Farghali., and Obsahuje bibliografii
Certain liver metabolic diseases point to the presence of disturbances in glycogen deposition. Epinephrine raises the cAMP level that activates protein kinase A leading to the activation of phosphorylase and glycogen breakdown. In the present report, we sought to investigate whether NO is produced during adrenoceptor agonist-induced glycogenolysis in rat hepatocytes in cultures. Isolated glycogen rich rat hepatocytes in cultures were used. NO production (NO2-) was assessed under the effect of adrenergic agonists and adrenergic agonist/antagonist pairs, dibutyryl cyclic AMP sodium-potassium salt (db-cAMP), NO synthase (NOS) inhibitors Nω-nitro-L-arginine methyl ester (L-NAME), aminoguanidine (AG) and the NO donor S-nitroso-N-acetyl penicillamine (SNAP) . The inducible NO synthase (iNOS) mRNA was examined by the reverse transcription-polymerase chain reaction (RT-PCR). Glycogenolysis was quantified by glucose levels released into medium. The amount of glucose and NO2- released by hepatocytes was increased as a result of epinephrine, phenylephrine or db-cAMP treatments. The increase in glucose and NO2- released by epinephrine or phenylephrine was blocked or reduced by prazosin pretreatment and by NOS inhibitors aminoguanidine and L-NAME. iNOS gene expression was up-regulated by epinephrine. It can be concluded that glycogenolysis occurs through α adrenoceptor stimulation and a signaling cascade may involve NO production., J. Hodis, N. Kutinová-Canová, P. Potměšil, L. Kameníková, E. Kmoníčková, Z. Zídek, H. Farghali., and Obsahuje biblografii a bibliografické odkazy