Vasopressin modulates K(+)-channel activities of cultured smooth muscle cells from porcine coronary artery

Abstract

The ATP-sensitive K+ channel (KATP channel) and the Ca(2+)-activated K+ channel (KCa channel) were active in cell-attached and excised inside-out patch configurations in cultured smooth muscle cells of the porcine coronary artery. Vasopressin activated the KCa channel (240 pS) when it was applied in the bath in the cell-attached patch mode presumably because of an increase in intracellular Ca2+, but it had no direct effect on the KCa channel. However, vasopressin directly blocked the KATP channel from outside the cell membranes in a concentration-dependent manner in both outside-out and cell-attached patch configurations; the K(+)-channel opener, nicorandil, reversed this effect. The KATP channel (30 pS) was highly active in the intact cell-attached patch configuration when the pipette contained a physiological concentration of Ca2+, suggesting that this channel may control the resting membrane potential. (The block might produce depolarization of the cells and might result in the contraction of smooth muscle cells.) These observations suggest that the KATP channel may play a role, at least in part, in controlling the contraction of smooth muscle cells of the coronary artery and that the control of vascular tone by vasopressin may be related to its ability to block the KATP channel.

Potassium channel activation and relaxation by nicorandil in rat small mesenteric arteries

“…Nicorandil has also been shown to activate ATP sensitive K + channels in cultured porcine coronary arterial cells and cells isolated from rat and rabbit portal vein. The unitary conductance is similar to that of the channel activated by nicorandil in cultured porcine coronary arterial cells (30 pS, Miyoshi et al, 1992;Wakatsuki et al, 1992), and of the channel activated by Figure 7 The inhibitory e ect of LY 83583 on nicorandil relaxations. (a) Concentration-response curves for relaxations to nicorandil under control conditions as in Figure 6a, and in the presence of LY 83583 at 10 nM (n=6), 100 nM (n=4), 1 mM (n=6), and 10 mM (n=4).…”

“…Clinically, in contrast to other nitrovasodilators, tolerance does not develop on continued application of nicorandil, and this lack of tolerance seems to be due its K + channel opening action (Frampton et al, 1992). K + current activation by nicorandil has been measured directly using patch clamp of smooth muscle cells cultured from porcine coronary artery (Miyoshi et al, 1992;Wakatsuki et al, 1992) and cells isolated from rat and rabbit portal vein (Kajioka et al, 1990;Kamouchi & Kitamura, 1994), but not so far in cells from small arteries. In both portal vein and coronary artery cells, nicorandil has been reported to activate channels that are inhibited by intracellular ATP (K ATP channels); in rat portal vein cells the channel activated by nicorandil has been reported to also be activated by intracellular Ca 2+ (Kajioka et al, 1990), while in rabbit portal vein cells the channel is activated by intracellular nucleoside diphosphates as well as inhibited by ATP (Kamouchi & Kitamura, 1994).…”

Long-lasting enhancement of synaptic excitability of CA1/subiculum neurons of the rat ventral hippocampus by vasopressin and vasopressin(4–8)

“…Suppression of the outward potassium current might also be expected to decrease the threshold and increase the number of action potentials triggered by EPSPs, an effect seen in several of the neurons tested. Vasopressin closes ATP-sensitive K ~ channels in cultured smooth muscle cells [74] and in insulin secreting cells [41]. This and other effects of VP on brain neurons, such as reversible depolarization, increase in input resistance and spontaneous activity, and activation of a voltage-dependent inward current [38,43,47,51,75], could thus be a result of different intracellular effector pathways being activated by these peptides via the same or different membrane receptors.…”

Nonendothelial‐derived nitric oxide activates the ATP‐sensitive K+ channel of vascular smooth muscle cells

“…The Kc, channel and KAT P channel have been observed mainly in cell-attached and inside-out patch configurations in the cultured smooth muscle ceils of porcine coronary artery [7,14]. Standen et al [15] showed that EDHF opens the KATP channel.…”