Apamin inhibits NO-induced relaxation of the spontaneous contractile activity of the myometrium from non-pregnant women

Reprod Biol Endocrinol. 2003 Feb 5;1:8. doi: 10.1186/1477-7827-1-8.


There is now considerable evidence for the involvement of K+ channels in nitric oxide (NO) induced relaxation of smooth muscles including the myometrium. In order to assess whether apamin-sensitive K+ channels play a role in NO - induced relaxation of the human uterus, we have studied the effect of specific blockers of these channels on the relaxation of myometrium from non-pregnant women. In vitro isometric contractions were recorded in uterine tissues from non-pregnant premenopausal women who had undergone hysterectomy. Apamin (10 nM) and scyllatoxin (10 nM) did not alter spontaneous myometrial contractions. However, 15-min pretreatment of the myometrium strips with apamin completely inhibited relaxation caused by diethylamine-nitric oxide (DEA/NO). The pretreatment with scyllatoxin significantly reduced (about 2.6 times) maximum relaxation of the strips induced by DEA/NO (p < 0.05). These results strongly suggest that, beside Ca2+ and voltage dependent charybdotoxin-sensitive (CTX-sensitive) K+ channels, apamin-sensitive K+ channels are also present in the human non-pregnant myometrium. These channels offer an additional target in the development of new tocolytic agents.

MeSH terms

  • Adult
  • Apamin / pharmacology*
  • Charybdotoxin / pharmacology
  • Female
  • Humans
  • Ion Channel Gating / drug effects
  • Ion Transport
  • Middle Aged
  • Muscle Relaxation / drug effects
  • Myometrium / drug effects*
  • Nitric Oxide / antagonists & inhibitors*
  • Potassium / metabolism
  • Potassium Channel Blockers / pharmacology*
  • Potassium Channels / drug effects*
  • Potassium Channels / physiology
  • Quaternary Ammonium Compounds / antagonists & inhibitors
  • Scorpion Venoms / pharmacology
  • Uterine Contraction / drug effects*


  • Potassium Channel Blockers
  • Potassium Channels
  • Quaternary Ammonium Compounds
  • Scorpion Venoms
  • apamin receptor
  • charybdotoxin receptor
  • diethylammonium-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate
  • Charybdotoxin
  • leiurotoxin I
  • Apamin
  • Nitric Oxide
  • Potassium