Pharmacologic actions of temiverine (p-INN) and its active metabolite, RCC-36, on isolated human urinary bladder muscle

Background: Temiverine (p-INN) is a newly synthesized drug that is expected to have anticholinergic action. We investigated the pharmacologic actions of temiverine and its active metabolite, RCC-36, on isolated human bladder.

Methods: Effects of temiverine and RCC-36 on the detrusor contractions induced by acetylcholine, potassium chloride (KCl), calcium chloride (CaCl2), and electric field stimulation were evaluated using the muscle-bath technique, and compared with the effects of atropine and oxybutynin.

Results: Atropine (10(-9) to 10(-6) mol/L), oxybutynin (10(-8) to 10(-5) mol/L), temiverine (10(-8) to 10(-5) mol/L), and RCC-36 (10(-8) to 3 x 10(-6) mol/L) caused a parallel shift to the right of the concentration-response curves to acetylcholine stimulation. The rank order of pA2 value was atropine > oxybutynin = RCC-36 > temiverine. Atropine did not suppress the maximum contractile response to acetylcholine, but the other drugs significantly suppressed this at the higher concentrations. Each drug caused a concentration-dependent inhibition of KCl (80 mmol/L)-, and CaCl2 (5 mmol/L)-induced contractile responses. Rank order of maximum inhibition was RCC-36 = temiverine > oxybutynin > atropine. Each drug caused a concentration-dependent inhibition of electric field-induced contraction with or without 10(-6) mol/L atropine pretreatment. Maximum inhibitions of temiverine and RCC-36 were significantly greater than that of oxybutynin.

Conclusion: Atropine, oxybutynin, temiverine, and RCC-36 have different efficacies and potencies of anticholinergic and calcium antagonistic activity on isolated human detrusor muscles. Furthermore, temiverine and RCC-36 have significant inhibitory actions toward the atropine-resistant part of contractions, which may be related to the calcium antagonistic actions of these compounds.