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Differences in ionic currents between myocardial and Purkinje cells of canine heart
Author(s) -
Vassalle Mario,
Bocchi Leonardo
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1053.5
Subject(s) - depolarization , heart cells , biophysics , myocyte , patch clamp , conductance , membrane potential , chemistry , electrophysiology , physics , biology , microbiology and biotechnology , neuroscience , condensed matter physics
Canine single ventricular muscle (VM) and Purkinje (P) cells were studied by means of whole cell patch clamp technique. In VM cells, slope conductance is greater and I K1 peak is less negative. In both P and VM cells, quick decay of step current with more negative depolarizing steps is blocked by Ba 2+ and disappears at less negative potentials. In VM cells, sodium currents I Na3 and I Na1 have less negative threshold potential. In both types of cells, I Na3 and I Na1 activations occur at I K1 peak, but in VM cells I Na1 is smaller. Slowly inactivating I Na2 is present in P cells and absent in VM cells, although a small short tail may follow I Na1 in some VM cells. I K1 peak is followed by early and late negative slope (NS) regions. In P cells, the early NS disappears with less negative holding potential (V h ). In VM cells, the late NS region is larger, peaks at positive potentials and persists with slow ramps or less negative V h . The NS region increases in size with faster ramps. In Vm cells, the NS early component is blocked by Ba 2+ and the late component by Ni 2+ . I Ca is greater in VM cells and I to in P cells. During repolarizing ramps, in VM cells the smaller outward current decreases less and in both M and P cells decreases more during faster ramps. A positive slope region is greater in VM cells and may be missing in some P cells. The many differences found are consistent with the different functions of P and VM cells in situ. Supported in part by NIH grant HL56092.