Прегледај по Аутор "Appiah, Isabella"

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    Effects of protamine sulphate on spontaneous and calcium-induced contractile activity in the rat uterus are potassium channels-mediated
    (Slovak Academy of Sciences, 2009) Oreščanin-Dušić, Zorana; Milovanović, Slobodan; Radojičić, Ratko; Nikolić-Kokić, Aleksandra; Appiah, Isabella; Slavić, Marija; Čutura, Neđo; Trbojević, Stevan; Spasić, Mihajlo; Blagojević, Duško
    Protamine sulphate (PS) effect on spontaneous and calcium-induced rhythmic contractions of isolated virgin rat uteri was studied. PS caused dose-dependent relaxation of both types of contractions (two-way ANOVA, significant dose effects). Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME; 10–5 mol/l), methylene blue (MB; 0.9 × 10–6 mol/l) or propranolol (1.7 × 10–5 mol/l) enhanced PS-mediated uterine muscle relaxation of spontaneous contractions. Dosedependent relaxation of spontaneous active isolated rat uterus with PS was lower in uteri pretreated with single dose of tetraethylammonium (TEA; 6 × 10–3 mol/l), glibenclamide (2 × 10–6 mol/l) and 4-aminopyridine (4-AP; 10–3 mol/l). Calcium-induced activity of the isolated rat uterus pretreated with the same concentration of L-NAME, MB, or propranolol modified the kinetic of PS-induced relaxation without changes in EC50 values. Pre-treatment with glibenclamide, TEA and 4-AP significantly reduce PS relaxing effect of calcium-induced activity and according to EC50 values the order of magnitude was glibenclamide > TEA > 4-AP. PS is mixture of polyamines and may activate different signal-transduction pathways. Our results cleary demonstrate that in uterine smooth muscle PS act dominantly through potassium chanels and marginaly through β-adrenergic receptos or nitric oxide-dependent pathways.
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    Reversible Oxidation ofMyometrial Voltage-Gated Potassium Channels with Hydrogen Peroxide
    (Hindawi, 2012) Appiah, Isabella; Nikolic-Kokic, Aleksandra; Orescanin-Dusic, Zorana; Radojicic, Ratko; Milovanovic, Slobodan; Spasic, Mihajlo; Blagojevic, Dusko
    The uteri, spontaneously active or Ca2+ (6mM) induced, were allowed to equilibrate, and to inhibit voltage-gated potassium (KV ) channels 1mM4-amino pyridine (4-AP) was applied for 15 min before addingH2O2 . H2O2 was added cumulatively: 2 μM, 20 μM, 200 μM, 400 μM, and 3mM. Average time for H2O2 concentrations (2, 20, 200, and 400) μM to reach its full effect was 15 min. H2O2 3mMhad a prolonged effect and therefore was left to act for 30 min. Two-way ANOVA showed significant differences in time dependency between spontaneous and Ca2+-induced rat uteri after applying 3mMH2O2 (type of contraction, P = 0.0280), but not 400 μMH2O2 (P = 0.9271). Our results indicate that H2O2 oxidises channel intracellular thiol groups and activates the channel, inducing relaxation. Cell antioxidative defence system quickly activates glutathione peroxidase (GSHPx) defence mechanism but not catalase (CAT) defence mechanism. Intracellular redox mechanisms repair the oxidised sites and again establish deactivation of KV channels, recuperating contractility. In conclusion, our results demonstrate that KV channels can be altered in a timedependent manner by reversible redox-dependent intracellular alterations.