title: Molecular basis of the T- and L-type Ca2+ currents in canine Purkinje fibres.
abstract: 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.
authors.affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, USA. brosati@notes.cc.sunysb.edu
authors.forename: Barbara
authors.initials: B
authors.lastname: Rosati
authors.forename: Wen
authors.initials: W
authors.lastname: Dun
authors.forename: Masanori
authors.initials: M
authors.lastname: Hirose
authors.forename: Penelope A
authors.initials: PA
authors.lastname: Boyden
authors.forename: David
authors.initials: D
authors.lastname: McKinnon
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000502:physiology*; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000502:physiology*; D004285:Dogs; D004594:Electrophysiology; D005786:Gene Expression Regulation; D017275:Isradipine / Q000494:pharmacology; D011690:Purkinje Fibers / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012604:Scorpion Venoms / Q000494:pharmacology; D016276:Ventricular Function
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; C419385:L-type calcium channel alpha(1C); D012333:RNA, Messenger; D012604:Scorpion Venoms; C118444:kurtoxin; D002118:Calcium; D017275:Isradipine