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ISSN 2522-9028 (Print)
ISSN 2522-9036 (Online)

Fiziologichnyi Zhurnal

is a scientific journal issued by the

Bogomoletz Institute of Physiology
National Academy of Sciences of Ukraine

Editor-in-chief: V.F. Sagach

The journal was founded in 1955 as
1955 – 1977 "Fiziolohichnyi zhurnal" (ISSN 0015 – 3311)
1978 – 1993 "Fiziologicheskii zhurnal" (ISSN 0201 – 8489)
1994 – 2016 "Fiziolohichnyi zhurnal" (ISSN 0201 – 8489)
2017 – "Fiziolohichnyi zhurnal" (ISSN 2522-9028)

Fiziol. Zh. 2007; 53(5): 67-74

Effect of paxilline on Ca2+-dependent K+ currentin smooth muscle cells isolated from rat vas deferens

D.O. Kryshtal, V.V. Nessin, M.F. Shuba

    O.O.Bogomoletz Institute of Physiology,National Academy of Sciences of Ukraine, Kyiv


The properties of the outward Ca2+-dependent K+ current (KCa) were investigated in single smooth muscle cells (SMCs) isolated from epididymal part of the rat vas deferens (RVD) using amphotericin B perforated patch-clamp technique. The complex kinetic of the net outward current elicited by positive voltage steps from -80 mV to +40 mV suggested the presence of several components of this current. KCa current was sepa- rated from the net outward current by removal of Ca2+ from the external solution. KCa was characterized by slow kinetics of current activation and decay. Mycotoxin paxilline, the se- lective blocker of the large conductance KCa channels, inhib- ited KCa current in a dose-dependent manner. At the concentration of 70 nM paxilline evoked 50% inhibition of KCa and at 1 mkM complete suppression of KCa current was achieved. The blocking effect of low concentrations of a non- selective KCa channels inhibitor tetraethylammonium (TEA) was compared to that of paxilline. The external application of 0,3 mM TEA inhibited KCa current similarly to 1 mkM of paxilline. Finally, we studied the effect of paxilline on the resting membrane potential of RVD SMCs. Paxilline (1 mkM) did not affect the membrane potential of SMCs with the rest- ing potential in the range of -60 to -40 mV. However, at poten- tials more positive than –40 mV application of paxilline sig- nificantly (up to 15 mV) depolarized the membrane of SMCs. These results suggest that the large conductance KCa channels in RVD SMCs do not contribute to the resting membrane potential but could serve as a hyperpolarizing mechanism at the significant membrane depolarizations.


  1. Повстян О.В., Зима О.В., Хархун М.І., Шуба М.Ф. Властивості харібдотоксинчутливого компонента кальційзалежного калієвого струму в гладень- ком’язових клітинах taenia coli морської свинки // Нейрофізіологія. – 2000. – 32, № 1. – С.16–21.
  2. Benham C.D., Bolton T.B., Lang R.J., Takewaki T. The mechanism of action of Ba2+ and TEA on single Ca2+- activated K+ channels in arterial and intestinal smooth muscle cell membranes // Pflug. Arch. – 1985. – 403, № 2. – P.120–127.
  3. Blatz A.L., MaglebyK.L. Ion conductance and selec- tivity of single calcium-activated potassium channels in cultured rat muscle // J. Gen. Physiol. – 1984. – № 1. – P.1–23.
  4. Farrugia G. Ionic conductances in gastrointestinal smooth muscles and interstitial cells of Cajal // Annu. Rev. Physiol. – 1999. – 61. – P.45–84.
  5. Goto K. Electrophysiological analysis of colchicine- induced supersensitivity in the rat vas deferens // J. Physiol. – 1980. – 308. – P.465–477.
  6. Harhun M.I., Jurkiewicz A., Jurkiewicz N.H., et al. Voltage-gated potassium currents in rat vas deferens smooth muscle cells // Pflug. Arch. – 2003. – 446(3). – P.380–386.
  7. Hong S.J., Roan Y.F., Chang C.C. Spontaneous activity of guinea pig ileum longitudinal muscle regulated by Ca(2+)-activated K+ channel // Amer. J. Physiol. – 1997. – 272(5 Pt. 1). – P.G962–G971.
  8. Knaus H., McManus O.B., Lee S.H. et al. Tremorgenic indole alkaloids potently inhibit smooth muscle high- conductance calcium-activated potassium channels // Biochemistry. – 1994. – 33(19). – P.5819–5828.
  9. 9. Kolb H.A. Potassium channels in excitable and non- excitable cells // Rev. Physiol. Biochem. Pharmacol. – 1990. – 115. – P.51–91.
  10. 10. Li G., Cheung D.W. Effects of paxilline on K+ channels in rat mesenteric arterial cells // Eur. J. Pharmacol. – 1999. – 372(1). – P.103–107.
  11. Sanchez M., McManus O.B. Paxilline inhibition of the alpha-subunit of the high-conductance calcium-activated potassium channel // Neuropharmacology. – 1996. – 35(7). – P.963–968.
  12. Schweitz H., Stansfeld C.E., Bidard J.N. et al. Charybdotoxin blocks dendrotoxin-sensitive voltage-ac- tivated K+ channels // FEBS Lett. – 1989. – 250(2). – P.519–522.
  13. Tammaro P., Smith A.L., Hutchings S.R. et al. Pharma- cological evidence for a key role of voltage-gated K+ channels in the function of rat aortic smooth muscle cells // Brit. J. Pharmacol. – 2004. – 143(2). – P.303–317.
  14. Yellen G. Ionic permeation and blockade in Ca2+-acti- vated K+ channels of bovine chromaffin cells // J. Gen. Physiol. – 1984. – № 2. – P.157–186.

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