AIM: To investigate the effect of rhubarb on contractile response of isolated gallbladder muscle strips from guinea pigs and its mechanism. METHODS: Guinea pigs were killed to remove the whole gallbladder. Two or three smooth muscle strips (8 mmx3 mm) were cut along the longitudinal direction. The mucosa on each strip was carefully removed. Each longitudinal muscle strip was suspended in a tissue chamber containing 5 mL Krebs solution (37 degrees C), bubbled continuously with 950 mL/L O-2 and 50 mL/L CO2. The resting tension (g), mean contractile amplitude (mm), and contractile frequency (waves/min) were simultaneously recorded on recorders. After 2-h equilibration, rhubarb (10, 20, 70, 200, 700, 1 000 g/L) was added cumulatively to the tissue chamber in turns every 2 min to observe their effects on gallbladder. Antagonists were given 3 min before administration of rhubarb to investigate the possible mechanism. RESULTS: Rhubarb increased the resting tension (from 0 to 0.40 +/- 0.02, P<0.001), and decreased the mean contractile amplitude (from 5.22 +/- 0.71 to 2.73 +/- 0.41, P<0.001). It also increased the contractile frequency of the gallbladder muscle strips in guinea pigs (from 4.09 +/- 0.46 to 6.08 +/- 0.35, P<0.001). The stimulation of rhubarb on the resting tension decreased from 3.98 +/- 0.22 to 1.58 +/- 0.12 by atropine (P<0.001), from 3.98 +/- 0.22 to 2.09 +/- 0.19 by verapamil (P<0.001) and from 3.98 +/- 0.22 to 2.67 +/- 0.43 by phentolamine (P<0.005). But the effect was not inhibited by hexamethonium (P>0.05). In addition, the action of mean amplitude and frequency was not inhibited by the above antagonists. CONCLUSION: Rhubarb can stimulate the motility of isolated gallbladder muscle strips from guinea pigs. The stimulation of rhubarb might be relevant with M receptor, Ca2+ channel and alpha receptor partly. (C) 2005 The WJG Press and Elsevier Inc. All rights reserved.
