title: Endothelin-1 enhances calcium entry through T-type calcium channels in cultured neonatal rat ventricular myocytes.
abstract: Endothelin-1 (ET-1), a 21-amino acid vasoconstrictive peptide, increases intracellular Ca2+ level and has hypertrophic action on ventricular myocytes. To elucidate a possible role of Ca2+ entry through sarcolemmal Ca2+ channels on this ET-1 action, we examined effects of ET-1 on L-type (ICa,L) and T-type (ICa,T) Ca2+ currents in cultured neonatal rat ventricular myocytes using the patch-clamp technique. ET-1 at a concentration of 10 nM increased the maximum current density of ICa,T from -3.0 +/- 1.4 microA/cm2 in the control condition to -4.4 +/- 1.6 microA/cm2 (p < 0.01). Although the peak amplitude of ICa,L was decreased during ET-1 application (from -9.7 +/- 1.9 microA/cm2 in the control condition to -5.0 +/- 1.4 microA/cm2 [p < 0.01]), this magnitude of decrease in ICa,T (52 +/- 19%) was comparable to that of spontaneous "run-down" of ICa,L (47 +/- 26%). The enhancement of ICa,T by ET-1 was dose dependent; it was initiated as low as 0.32 nM, and the maximal response was attained at approximately 10 nM, with a half-maximal dose of 1.26 nM. The enhancement of ICa,T by ET-1 was antagonized by protein kinase C inhibitors staurosporine (0.2 microM) and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7, 20 microM) applied to the pipette solution. Extracellular application of tumor-promoting phorbol esters, phorbol 12,13-dibutyrate (PDBu) and 4 beta-phorbol 12-myristate 13-acetate, augmented ICa,T. PDBu (0.2 microM) increased the maximal current density of ICa,T from -4.2 +/- 0.5 microA/cm2 in the control condition to -5.5 +/- 1.0 microA/cm2 (p < 0.01). In the presence of H-7 (20 microM) in the pipette solution, PDBu failed to enhance ICa,T, and an inactive isomer of PDBu (4 alpha-phorbol 12,13-dibutyrate, 0.2 microM) did not augment ICa,T. Thus, ET-1 enhances Ca2+ entry through the sarcolemmal T-type Ca2+ channel, possibly through a pathway involving activation of protein kinase C. This ET-1 action may be involved in the rise of the intracellular Ca2+ level and may contribute to the induction of cardiac hypertrophy by ET-1.
authors.affiliation: Department of Cardiovascular Diseases, Tokyo Medical and Dental University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Furukawa
authors.forename: H
authors.initials: H
authors.lastname: Ito
authors.forename: J
authors.initials: J
authors.lastname: Nitta
authors.forename: M
authors.initials: M
authors.lastname: Tsujino
authors.forename: S
authors.initials: S
authors.lastname: Adachi
authors.forename: M
authors.initials: M
authors.lastname: Hiroe
authors.forename: F
authors.initials: F
authors.lastname: Marumo
authors.forename: T
authors.initials: T
authors.lastname: Sawanobori
authors.forename: M
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D002478:Cells, Cultured; D004594:Electrophysiology; D016232:Endothelins / Q000494:pharmacology*; D004789:Enzyme Activation; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D051381:Rats
chemical_list: D015220:Calcium Channels; D016232:Endothelins; D047428:Protein Kinase Inhibitors; D006160:Guanosine Triphosphate; D011493:Protein Kinase C; D002118:Calcium