1984 年 36 巻 1 号 p. 153-159
The longitudinal muscle strip of portal vein, excised from adult wistar rat weighing 200 to 250g, was suspended in an organ bath (50m1) containing Locke's solution saturated with pure oxygen at 37°C (pH: 7.4); 0.5g of initial tension was loaded to the preparation and the change of tension produced by the drug was isometrically recorded. Effects of guanethidine were studied on spontaneous contractions, potassium-depolarized contraction and calcium-induced contraction after potassium-depolarization in the preparation. The results obtained were as follows.1) Guanethidine in a low concentration of 2.5 X 10-6 g/ml enhanced the tensio n developement induced by high potassium-Locke's solution and by calcium chloride which was added to the potassium depolarized preparation.2) Acetylcholine and noradrenaline induced contraction of the preparation, of which contraction was enhanced by the presence of guanethidine (1.25 to 2.5 x 10-6 g/m1). From the results, it was assumed that guanethidine may posses s an action to increase the permeability or inflow of calcium ions through the smooth muscle membrane in the rat portal vein.