Key result
Cav3.2 predominantly encodes Purkinje cell T-type Ca2+ channels, while Cav1.3 contributes minimally to L-type currents.
Why the study?
The molecular identity of T-type and L-type Ca2+ currents in canine Purkinje cells was not fully characterized.
This preclinical study identifies Ca(v)3.2 as the primary molecular basis for T-type calcium currents in canine Purkinje cells.
Identifies Cav3.2 as dominant T-type channel in canine Purkinje cells; leaves open translation to human arrhythmias or therapy.
This study examines the molecular basis for the T-type and L-type Ca(2+) currents in canine Purkinje cells. The I(CaT) in Purkinje cells was completely suppressed by 200 nM kurtoxin, a specific blocker of both Ca(v)3.1 and Ca(v)3.2 channels. Since only Ca(v)3.2 mRNA is expressed at high levels in Purkinje fibres, being approximately 100-fold more abundant than either Ca(v)3.1 or Ca(v)3.3 mRNAs, it is concluded that the Ca(v)3.2 gene encodes the bulk of the T-type Ca(2+) channels in canine Purkinje cells. This conclusion is consistent with the sensitivity of the current to blockade by Ni(2+) ions (K(D) = 32 microM). For L-type channels, Ca(v)1.2 mRNA was most abundant in Purkinje fibres but a significant level of Ca(v)1.3 mRNA expression was also found. A comparison of the sensitivity to blockade by isradipine of the L-type currents in Purkinje cells and ventricular epicardial myocytes, which only express Ca(v)1.2, suggests that the Ca(v)1.3 channels make, at most, a minor contribution to the L-type current in canine Purkinje cells.
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Rosati et al. (2007) studied this question. Kurtoxin, Ni2+ ions, and isradipine was evaluated on Molecular basis of T-type and L-type Ca2+ currents. The Cav3.2 gene encodes the bulk of T-type Ca2+ channels in canine Purkinje cells, while Cav1.3 channels make a minor contribution to L-type currents compared to Cav1.2.
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