The effects of caffeine on ATP-sensitive K+ channels in smooth muscle cells from pig urethra

Noriyoshi Teramoto, Takakazu Yunoki, Kiyoshi Tanaka, Makoto Takano, Ichiro Masaki, Yoshikazu Yonemitsu, Katsuo Sueishi, Yushi Ito

Research output: Contribution to journalArticle

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Abstract

1 The effects of caffeine on both levcromakalim-induced macroscopic and unitary currents in pig proximal urethra were investigated by the use of patch-clamp techniques (conventional whole-cell configuration and cell-attached configuration). The effects of caffeine were also examined on currents in inside-out patches of COS7 cells expressing carboxy terminus truncated inwardly rectifying K+ channel (Kir6.2) subunits (i.e. Kir6.2ΔC36) which form ATP-sensitive K+ channels (K(ATP) channels). 2 In conventional whole-cell configuration, the levcromakalim (100 μM)-induced inward current (symmetrical 140 mM K+ conditions) was inhibited by caffeine (≥1 mM) at a holding potential of -50 mV. In contrast, ryanodine (10 μM) caused no significant inhibitory effect on the gradual decay of the levcromakalim-induced current at -50 mV. 3 The amplitude of the 30 μM levcromakalim-induced current was enhanced by 3-isobutyl-1-methylxanthine (IBMX, 100 μM). 4 In cell-attached configuration, the levcromakalim-induced K+ channel openings were inhibited by subsequent application of 10 mM caffeine, decreasing the channel open probability at -50 mV. 5 Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of Kir6.2 transcript in pig urethra. 6 Caffeine (≥3 mM) inhibited the channel activity of Kir6.2ΔC36 expressed in COS7 cells (3 mM caffeine, 65 ± 6%, n = 4; 10 mM caffeine, 29 ± 2%, n = 4). 7 These results suggest that caffeine can inhibit the activity of K(ATP) channels through a direct blocking effect on the pore-forming Kir subunit.

Original languageEnglish
Pages (from-to)505-513
Number of pages9
JournalBritish Journal of Pharmacology
Volume131
Issue number3
DOIs
Publication statusPublished - Jan 1 2000

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Urethra
Caffeine
Smooth Muscle Myocytes
Cromakalim
Swine
Adenosine Triphosphate
1-Methyl-3-isobutylxanthine
Inwardly Rectifying Potassium Channel
Ryanodine
Patch-Clamp Techniques
Reverse Transcriptase Polymerase Chain Reaction

All Science Journal Classification (ASJC) codes

  • Pharmacology

Cite this

The effects of caffeine on ATP-sensitive K+ channels in smooth muscle cells from pig urethra. / Teramoto, Noriyoshi; Yunoki, Takakazu; Tanaka, Kiyoshi; Takano, Makoto; Masaki, Ichiro; Yonemitsu, Yoshikazu; Sueishi, Katsuo; Ito, Yushi.

In: British Journal of Pharmacology, Vol. 131, No. 3, 01.01.2000, p. 505-513.

Research output: Contribution to journalArticle

Teramoto, N, Yunoki, T, Tanaka, K, Takano, M, Masaki, I, Yonemitsu, Y, Sueishi, K & Ito, Y 2000, 'The effects of caffeine on ATP-sensitive K+ channels in smooth muscle cells from pig urethra', British Journal of Pharmacology, vol. 131, no. 3, pp. 505-513. https://doi.org/10.1038/sj.bjp.0703586
Teramoto, Noriyoshi ; Yunoki, Takakazu ; Tanaka, Kiyoshi ; Takano, Makoto ; Masaki, Ichiro ; Yonemitsu, Yoshikazu ; Sueishi, Katsuo ; Ito, Yushi. / The effects of caffeine on ATP-sensitive K+ channels in smooth muscle cells from pig urethra. In: British Journal of Pharmacology. 2000 ; Vol. 131, No. 3. pp. 505-513.
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