[Effects of bazheng mixture on urinary amount and contractile-relaxant function of isolated urethral smooth muscle in rabbits].

Objective: To explore the pharmacological mechanism of Bazheng Mixture (BZM) in promoting diuresis and relieving stranguria.

Methods: By means of urine collection through indwelling catheter and urethral ring isolation test to observe the effects of BZM on the urinary amount of conscious rabbits and contractile-relaxant function of urethral smooth muscle isolated from rabbits.

Results: BZM, at dosage of 5.0 g/kg or 10.0 g/kg by gastrogavage, could increase the urinary amount in 60 min obviously (P < 0.05). For the isolated urethral rings, the maximal contractile and maximal relaxant forces reduced significantly (P < 0.05 or P < 0.01) when the concentration of BZM applied ranged between 9.9-90.9 g/L; the frequency increased significantly (P < 0.05 or P < 0.01) when the concentration ranged 29.1-90.9 g/L and the amplitude increased significantly when the concentration were 56.6 and 90.0 g/L. Along with the concentration of BZM increased from 9.9 g/L to 90.9 g/L, the changes occurred in the above-mentioned parameters of urethral ring were in order of potency amplitude > frequency > maximal relaxant force > maximal contractile force.

Conclusion: The effects of BZM in enhancing urethral peristalsis may be stronger than that in dilating the urethral caliber. Its mechanism in promoting diuresis and relieving stranguria may be related with its action of urethral dilatation and potential peristalsis promotion.