L, P-/Q- and T-type Ca2+ channels in smooth muscle cells from human umbilical artery.
The electrophysiological and pharmacological properties of Ca(2+) current (I(Ca)) were determined by the whole-cell configuration of the patch-clamp technique in smooth muscle cells from human umbilical artery. Using 5 mM extracellular Ca(2+), depolarizing step pulses from -60 to 50 mV from a holding membrane potential of -80 mV evoked an I(Ca) which activated at membrane potentials more positive than -50 mV and exhibited a maximum current density in a range of 10-20 mV. Steady-state inactivation protocols using a V(test) of 10 mV gave a voltage at one-half inactivation and a slope factor of -35.6 mV and 9.5 mV, respectively. Nifedipine (1 microM), an L-type Ca(2+) channels antagonist, completely inhibited I(Ca), while the L-type Ca(2+) channels agonist Bay-K 8644 (1 microM) significantly increased I(Ca) amplitude. Moreover, the selective blocker of P-/Q-type Ca(2+) channels omega-agatoxin IVA partially blocked I(Ca) (about 40 % inhibition at +20 mV by 20 nM). These pharmacological results suggest that L- and P-/Q-type Ca(2+) channels, both nifedipine-sensitive, underlie the I(Ca) registered using low extracellular Ca(2+). The presence of the P-/Q-type Ca(2+) channels was confirmed by immunoblot analysis. When I(Ca) was recorded in a high concentration (30 mM) of extracellular Ca(2+) or Ba(2+) as current carrier, it was evident the presence of a nifedipine-insensitive component which completely inactivated during the course of the voltage-step (75 ms) at all potentials tested, and was blocked by the T-type Ca(2+) channels blocker mibefradil (10 microM). Summarizing, this work shows for the first time the electrophysiological and pharmacological properties of voltage-activated Ca(2+) currents in human umbilical artery smooth muscle cells.
Salemme
Silvia
S
Cátedra de Fisiología, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina.
Rebolledo
Alejandro
A
Speroni
Francisco
F
Petruccelli
Silvana
S
Milesi
Verónica
V
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020865:Calcium Channels, P-Type / Q000378:metabolism; D020907:Calcium Channels, Q-Type / Q000378:metabolism; D020747:Calcium Channels, T-Type / Q000378:metabolism; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011247:Pregnancy; D014469:Umbilical Arteries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020867:omega-Agatoxin IVA / Q000494:pharmacology
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D020747:Calcium Channels, T-Type; D020867:omega-Agatoxin IVA; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine