Properties of voltage-gated Ca(2+) channels in rabbit ventricular myocytes expressing Ca(2+) channel alpha(1E) cDNA.
Using the whole-cell patch-clamp technique, we have studied the properties of alpha(1E) Ca(2+) channel transfected in cardiac myocytes. We have also investigated the effect of foreign gene expression on the intrinsic L-type current (I(Ca,L)). Expression of green fluorescent protein significantly decreased the I(Ca,L). By contrast, expression of alpha(1E) with beta(2b) and alpha(2)/delta significantly increased the total Ca(2+) current, and in these cells a Ca(2+) antagonist, PN-200-110 (PN), only partially blocked the current. The remaining PN-resistant current was abolished by the application of a low concentration of Ni(2+) and was little affected by changing the charge carrier from Ca(2+) to Ba(2+) or by beta-adrenergic stimulation. On the basis of its voltage range for activation, this channel was classified as a high-voltage activated channel. Thus the expression of alpha(1E) did not generate T-like current in cardiac myocytes. On the other hand, expression of alpha(1E) decreased I(Ca,L) and slowed the I(Ca,L) inactivation. This inactivation slowing was attenuated by the beta(2b) coexpression, suggesting that the alpha(1E) may slow the inactivation of I(Ca,L) by scrambling with alpha(1C) for intrinsic auxiliary beta.
Tateyama
M
M
Department of Physiology, Juntendo University School of Medicine, Tokyo 113-8421, Japan.
Zong
S
S
Tanabe
T
T
Ochi
R
R
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018076:DNA, Complementary / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D017930:Genes, Reporter / Q000502:physiology; D049452:Green Fluorescent Proteins; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007202:Indicators and Reagents / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D017275:Isradipine / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D009532:Nickel / Q000494:pharmacology; D011817:Rabbits; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D018076:DNA, Complementary; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D018342:Receptors, Adrenergic, beta-1; D049452:Green Fluorescent Proteins; D009532:Nickel; D007545:Isoproterenol; D017275:Isradipine