Evaluation of genes encoding for the transient outward current (Ito) identifies the KCND2 gene as a cause of J-wave syndrome associated with sudden cardiac death.

Background: J-wave ECG patterns are associated with an increased risk of sudden arrhythmic death, and experimental evidence supports a transient outward current (I(to))-mediated mechanism of J-wave formation. This study aimed to determine the frequency of genetic mutations in genes encoding the I(to) in patients with J waves on ECG.

Methods And Results: Comprehensive mutational analysis was performed on I(to)-encoding KCNA4, KCND2, and KCND3 genes, as well as the previously described J-wave-associated KCNJ8 gene, in 51 unrelated patients with ECG evidence defining a J-wave syndrome.

Effects of the endogenous cannabinoid anandamide on voltage-dependent sodium and calcium channels in rat ventricular myocytes.

Background And Purpose: The endocannabinoid anandamide (N-arachidonoyl ethanolamide; AEA) exerts negative inotropic and antiarrhythmic effects in ventricular myocytes.

Experimental Approach: Whole-cell patch-clamp technique and radioligand-binding methods were used to analyse the effects of anandamide in rat ventricular myocytes.

Key Results: In the presence of 1-10 μM AEA, suppression of both Na(+) and L-type Ca(2+) channels was observed.

Lanthanum suppresses arachidonic acid-induced cell death and mitochondrial depolarization in PC12 cells.

Within the framework of studying the mechanisms of acute toxicity of arachidonic acid and the role of ambient cations, we have investigated the effects of extracellular La(3+) on arachidonic acid-induced death (lactate dehydrogenase release) and mitochondrial depolarization (rhodamine 123 fluorescence) in PC12 cells. Micromolar La(3+) profoundly suppressed arachidonic acid toxicity and this effect was dependent on the presence of other cations. Whereas in the cation-free solution 10-20 microM La(3+) protected most cells from death caused by a 2 hour-long exposure to 20 microM arachidonic acid, the cytoprotective effect of 100 microM La(3+) was reduced to approximately 70% in the presence of a normal complement of monovalent cations and was hardly detectable with 5 mM Ca(2+) in the bath.

The glutathione reductase inhibitor carmustine induces an influx of Ca2+ in PC12 cells.

We studied the effects of carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea) on the intracellular Ca(2+) concentration ([Ca(2+)](i)) in PC12 cells using fura-2 fluorescence imaging. Carmustine (100 microM) caused a delayed increase in [Ca(2+)](i) that developed within approximately 3 h. This effect was enhanced in cells that were pretreated with an inhibitor of glutathione (GSH) synthesis, buthionine sulfoximine (BSO, 200 microM, 24 h), and was suppressed in cells that were treated with an antioxidant deferoxamine (50 microM).

Ca2+ influx is not involved in acute cytotoxicity of arachidonic acid.

Arachidonic acid (AA; 20:4, n-6) has been implicated in cell damage in the brain under ischemia-reperfusion and other pathological conditions. In our experiments, PC12 cells exposed to >10 microM AA died within 1-2 hr, as assessed by the LDH release assay. Since AA is known to induce Ca2+/cation-permeable conductance in the plasma membrane, we investigated whether Ca2+ influx plays a role in this acute cell death.

Ion dependence of cytotoxicity of carmustine against PC12 cells.

Cytotoxicity is a major complication of carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, BCNU) therapy for treatment of brain tumors and lymphomas. Using the lactate dehydrogenase (LDH) cell death assay in PC12 cells, we studied the role in this phenomenon of transmembrane ion fluxes that could be activated following inhibition by carmustine of glutathione reductase. The cytotoxic effect of carmustine developed during 4-6 h, with the EC50 of 27 microM.