[Effects of vitamin K3 on the contractile activity of the colonic smooth muscles of guinea pig through the calcium activated potassium channel].
OBJECTIVE
To study the mechanism of relaxation of gastrointestinal smooth muscles by vitamin K(3).


METHODS
Stripes of proximal colon were collected from guinea pigs. Suspension of single cells was created from these stripes. TD-112S transducer was used to measure the contraction of the stripes stimulated by vitamin K(3) of the concentrations of 40, 100, 400, and 800 micromol/L respectively. The Ca(2+)-activated K(+) current [IK(Ca)] of the cytomembrane of the colon smooth muscle was recorded with an EPC 10 amplifier under conventional whole cell patterns.


RESULTS
The contraction frequencies of the muscle stripes stimulated by vitamin K(3) of the concentrations of 40, 100, 400, and 800 micromol/L were 79% +/- 4%, 58% +/- 5%, 33% +/- 4%, and 12% +/- 3% respectively of that of the control group (all P < 0.01), and the contraction strength was reduced to 77% +/- 10%, 54% +/- 7%, 30% +/- 6%, and 11% +/- 4% respectively (all P < 0.01). The IK((Ca)) of the cytomembrane of the colon smooth muscle at the voltage of +60 mV was increased to 120% +/- 18%, 149% +/- 12%, 197% +/- 19%, and 223% +/- 14% respectively (all P < 0.01).


CONCLUSIONS
Vitamin K(3) inhibits the contractile activity of the colonic muscle stripes and increases the IK(Ca) of single myocytes concentration-dependently. The mechanism is activation of the Ca(2+)-activated K(+) channel, thus promoting the potassium efflux.
Li
Jun
J
Department of Gastroenterology, People's Hospital of Wuhan University, Wuhan 430060, China.
Luo
He-sheng
HS
He
Xiao-gu
XG
D000818:Animals; D003106:Colon; D006168:Guinea Pigs; D009119:Muscle Contraction / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects*; D024483:Vitamin K 3 / Q000494:pharmacology*
D024681:Potassium Channels, Calcium-Activated; D024483:Vitamin K 3