Characterization of voltage‐gated calcium currents in freshly isolated smooth muscle cells from rat tail main artery

Abstract

The aim of the present study was to characterize voltage-gated Ca2+ currents in smooth muscle cells freshly isolated from rat tail main artery in the presence of 5 mmol L(-1) external Ca2+. Calcium currents were identified on the basis of their voltage dependencies and sensitivity to nifedipine, Ni2+ and cinnarizine. In the majority of the cells studied, T- and L-type currents were observed, while the remaining cells showed predominantly L-type currents. In the latter group of cells, holding potential change from -50 to either -70 or -90 mV increased the corresponding inward current amplitude while its voltage activation threshold remained unchanged. The steady state inactivation of L-type Ca2+ channels showed half-maximal inactivation at -38 mV. A Ca2+-dependent inactivation was also evident. Nifedipine (3 micromol L(-1)) blocked L-type but not T-type Ca2+ currents. Ni2+ (50 micromol L(-1)) as well as cinnarizine (1 micromol L(-1)) suppressed the nifedipine-resistant, T-type component of the currents. At higher concentrations, both Ni2+ (0.3-1 mmol L(-1)) and cinnarizine (10 micromol L(-1)) blocked the net inward current. Replacement of Ca2+ with 10 mmol L(-)1 Ba2+ significantly increased the amplitude of L-type Ca2+ currents. These results demonstrate that smooth muscle cells freshly isolated from rat tail main artery may be divided into two populations, one expressing both L- and T-type and the other only L-type Ca2+ channels. Furthermore, this report shows that in arterial smooth muscle cells cinnarizine potently inhibited T-type currents at low concentrations (1 micromol L(-1)) but also blocked L-type Ca2+ currents at higher concentrations (10 micromol L(-1)).

Role of constitutively expressed heme oxygenase-2 in the regulation of guinea pig coronary artery tone

“…Cinnarizin, known as a blocker of vascular L-and T-type voltage-sensitive Ca 2+ channels [22], caused a reduction in the vascular tone in the presence of hemin, the difference being statistically significant at 10 M hemin (Fig. 2).…”

Molecular Physiology of Low-Voltage-Activated T-type Calcium Channels

“…LVA currents have been found in the following arterial SMCs: coronary (130,281,332), aortic (3), mesenteric (150,311,372), rabbit ear (34), rat tail (327,428), and middle cerebral arterioles (167). RT-PCR detected the expression of both Ca v 3.1 and Ca v 3.2 in rat mesenteric arterioles (150).…”

Cardamonin Is a Bifunctional Vasodilator that Inhibits Cav1.2 Current and Stimulates KCa1.1 Current in Rat Tail Artery Myocytes

“…At this point, the various protocols were performed as detailed below. Both I Ba(L) and I Ca(L) did not run down over the next 20 to 30 min under these conditions (Petkov et al, 2001).…”

“…Cells used in this study expressed Ca v 1.2 but not Ca v 3.1 channels (see Petkov et al, 2001 Current was elicited with 250-ms clamp pulses (0.067 Hz), either to 0 mV or to 10 mV, from a V h of Ϫ80 mV until a stable current response was achieved (usually 7-10 min after the whole-cell configuration had been obtained). At this point, the various protocols were performed as detailed below.…”