title: Cyclic AMP and cyclic GMP independent stimulation of ventricular calcium current by peroxynitrite donors in guinea pig myocytes.
abstract: We investigated the potential involvement of peroxynitrite (ONOO(-)) in the modulation of calcium current (I(Ca)) in guinea pig ventricular myocytes with the whole-cell patch clamp technique and with cyclic AMP (cAMP) measurements. Because of the short half-life of ONOO(-) at physiological pH, we induced an increase in its intracellular levels by using donors of the precursors, nitric oxide (NO) and superoxide anion (O(2) (-)). High concentrations of NO donors, SpermineNONOate (sp/NO, 300 microM) or SNAP (300 microM) increased basal I(Ca) (50.3 +/- 4.6%, n = 7 and 46.2 +/- 5.0%, n = 13). The superoxide anion donor Pyrogallol (100 microM) also stimulated basal I(Ca) (44.6 +/- 2.8%, n = 11). At lower concentration sp/NO (10 nM) and Pyrogallol (1 microM), although separately ineffective on I(Ca), enhanced the current if applied together (33.5 +/- 0.7%, n = 7). The simultaneous donor of O(2) (-) and NO, SIN-1 (500 microM), also stimulated basal I(Ca) (22.8 +/- 2.1%, n = 13). In the presence of saturating cyclic GMP (cGMP, 50 microM) in the patch pipette or of extracellular dibutyryl cGMP (dbcGMP, 100 microM), I(Ca) was still increased by SIN-1 (32.0 +/- 6.1%, n = 4 and 30.0 +/- 5.4%, n = 8). Both Manganese(III)tetrakis(4-benzoic acid) porphyrin chloride (MnTBAP, 100 microM) a ONOO(-) scavenger, and superoxide dismutase (SOD) (150 U/ml) reversed the stimulatory effect of SIN-1 on I(Ca) (respectively -0.6 +/- 4.1%, n = 4 and 3.6 +/- 4.3%, n = 4). Intracellular cAMP level was unaltered by SIN-1, while it was enhanced by blocking the NO-cGMP pathway with the NO synthase inhibitor L-NMMA. These results suggest that peroxynitrite donors increase cardiac calcium current without the involvement of cAMP and cGMP.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism*; D008665:Metalloporphyrins / Q000494:pharmacology; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D030421:Peroxynitrous Acid / Q000378:metabolism*; D011748:Pyrogallol / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D015220:Calcium Channels; D008665:Metalloporphyrins; D020030:Nitric Oxide Donors; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D011748:Pyrogallol; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine; D000242:Cyclic AMP; D013482:Superoxide Dismutase; D006152:Cyclic GMP; D002118:Calcium