Juvenile pig detrusor: Effects of propiverine and three of its metabolites

Phasic contractions in urinary bladder from juvenile versus adult pigs

Aims

Alterations in properties of the bladder with maturation are relevant physiologically and pathophysiologically. The aim of this study was to investigate alterations in bladder properties with maturation in juvenile vs. adult pig, focussing on differences between layers of the bladder wall (mucosa vs. detrusor) and the presence and functional contribution of interstitial cells (ICs).

Methods

Basal and cholinergic-induced phasic contractions (PCs) in mucosal and denuded-detrusor strips from juvenile and adult pigs were assessed. Expression of c-kit, a marker of ICs, was investigated in the mucosa and the detrusor layers of the pig bladder. The functional role of ICs in mediating PCs was examined using imatinib.

Results

Mucosal strips from juvenile and adult pig bladders demonstrated basal PCs whilst denuded-detrusor strips did not. PCs of mucosal strips from juvenile pigs were significantly greater than those from adult bladders. Immunoreactivity for c-kit was detected in mucosa and detrusor layers of pig bladder. Histological studies demonstrated a distinct layer of smooth muscle between the urothelium and bladder detrusor, termed the muscularis mucosa. Imatinib was only effective in inhibiting PCs in mucosal strips from juvenile pigs. Imatinib inhibited the carbachol-induced PCs of both juvenile and adult denuded-detrusor strips, although strips from juvenile bladders demonstrated a trend towards being more sensitive to this inhibition.

Conclusions

We confirm the presence of c-kit positive ICs in pig urinary bladder. The enhanced PCs of mucosal strips from juvenile animals could be due to altered properties of ICs or the muscularis mucosa in the bladders of these animals.

The muscarinic receptor antagonist propiverine exhibits α(1)-adrenoceptor antagonism in human prostate and porcine trigonum

Purpose

Combination therapy of male lower urinary tract symptoms with α₁-adrenoceptor and muscarinic receptor antagonists attracts increasing interest. Propiverine is a muscarinic receptor antagonist possessing additional properties, i.e., block of L-type Ca²⁺ channels. Here, we have investigated whether propiverine and its metabolites can additionally antagonize α₁-adrenoceptors.

Methods

Human prostate and porcine trigone muscle strips were used to explore inhibition of α₁-adrenoceptor-mediated contractile responses. Chinese hamster ovary (CHO) cells expressing cloned human α₁-adrenoceptors were used to determine direct interactions with the receptor in radioligand binding and intracellular Ca²⁺ elevation assays.

Results

Propiverine concentration-dependently reversed contraction of human prostate pre-contracted with 10 μM phenylephrine (−log IC₅₀ [M] 4.43 ± 0.08). Similar inhibition was observed in porcine trigone (−log IC₅₀ 5.01 ± 0.05), and in additional experiments consisted mainly of reduced maximum phenylephrine responses. At concentrations ≥1 μM, the propiverine metabolite M-14 also relaxed phenylephrine pre-contracted trigone strips, whereas metabolites M-5 and M-6 were ineffective. In radioligand binding experiments, propiverine and M-14 exhibited similar affinity for the three α₁-adrenoceptor subtypes with −log K_i [M] values ranging from 4.72 to 4.94, whereas the M-5 and M-6 did not affect [³H]-prazosin binding. In CHO cells, propiverine inhibited α₁-adrenoceptor-mediated Ca²⁺ elevations with similar potency as radioligand binding, again mainly by reducing maximum responses.

Conclusions

In contrast to other muscarinic receptor antagonists, propiverine exerts additional L-type Ca²⁺-channel blocking and α₁-adrenoceptor antagonist effects. It remains to be determined clinically, how these additional properties contribute to the clinical effects of propiverine, particularly in male voiding dysfunction.

Anticholinergic effects of cis- and trans-isomers of two metabolites of propiverine

The muscarinic receptor antagonist propiverine used for therapy of overactive bladder undergoes first pass metabolism, leading to several active metabolites, which affect muscarinic receptors and L-type Ca(2+) channels with different potencies. M-5, the major metabolite in blood, and M-6 can be synthesized as cis- and trans-isomers. We systematically investigated the pharmacodynamic profiles of the isomers on detrusor contractile function. In murine and porcine detrusor, the effects of the derivatives were examined on contractions induced by electric field stimulation (EFS), cumulatively increasing concentrations of carbachol or high KCl concentration. EFS contractions were concentration-dependently reduced by the M-5 and M-6 isomers although to a different extent. M-5(cis) was slightly more potent than M-5(trans), but the differences did not reach statistical significance. M-6(cis) was significantly more potent than M-6(trans). Responses to carbachol were antagonized by all compounds due to rightward shifts of the concentration-response curves, but only M-5(trans) also significantly reduced the maximum response. pK (B) values obtained with Schild plot analysis indicated slightly higher potency for M-6(cis) than M-6(trans). Ca(2+) influx-dependent contractions elicited by K(+) depolarization were less impaired by low concentrations of the M-6 isomers, but strongly suppressed by 100 microM of the M-5 isomers, suggesting an additional effect of the two M-5 isomers on Ca(2+) influx. All investigated isomers of M-5 and M-6 are biologically active in reducing detrusor contraction in animal tissue. While M-5( cis,) M-6(cis), and M-6(trans) possess surmountable or partially surmountable antagonistic properties at muscarinic receptors, M-5(trans) is a strong non-competitive antagonist. However, at higher concentration ranges, all four compounds seem to have additional effects on Ca(2+) influx.

Efficacy, tolerability and safety of propiverine hydrochloride in comparison to oxybutynin in children with urge incontinence due to overactive bladder: Results of a multicentre observational cohort study

OBJECTIVE

To compare, in a retrospective observational cohort study, the efficacy, tolerability and safety of propiverine and oxybutynin in children with urge incontinence (UI) due to overactive bladder.

PATIENTS AND METHODS

Medical records were scrutinized for children with UI. As a primary efficacy outcome variable the achievement of continence after treatment with variable doses of propiverine or oxybutynin was assessed. Weekly UI episodes and daily voiding frequency were evaluated as secondary efficacy outcomes. Tolerability was evaluated by the rate of adverse events, adverse drug reactions caused by antimuscarinics and premature treatment termination.

RESULTS

At 16 study centres, 621 children aged 5-14 years with UI due to overactive bladder were enrolled. After anticholinergic treatment (437 propiverine, 184 oxybutynin) continence was achieved in 61.6% and 58.7% of the patients after 186 and 259 days, respectively. There were clinically relevant improvements in voiding frequency across treatment groups. Daily doses of propiverine were markedly below the recommendations (0.54 vs 0.8 mg/kg body weight), daily doses of oxybutynin were according to the recommendations (0.31 vs 0.2-0.4 mg/kg body weight) at treatment initiation. There was a significantly more favourable tolerability to propiverine than oxybutynin for the overall rate of adverse events (3.9% vs 16.3%, odds ratio 4.813), adverse drug reactions caused by propiverine or oxybutynin (2.8% vs 9.2%) and premature treatment termination due to adverse drug reactions (1.6% vs 4.4%).

CONCLUSION

Propiverine and oxybutynin are effective in children with UI due to overactive bladder. Sufficient treatment periods of at least 2, preferably 3-4, months are the crucial factors for a successful treatment. The tolerability profile of propiverine is better than for oxybutynin.

Urothelial effects of oral agents for overactive bladder

The cholinergic system of the bladder includes muscarinic receptors distributed to detrusor myocytes and structures within mucosa including bladder afferent (sensory) nerves. The receptors have been shown to be involved in afferent signaling from the bladder, but it has not been established to what extent effects on this mucosal signaling pathway contribute to the therapeutic efficacy of the clinically used antimuscarinics. Mucosa can be influenced by antimuscarinics via the bloodstream. However, some antimuscarinics and their active metabolites are excreted in urine in amounts that may affect the mucosal muscarinic receptors from the luminal side. This has not yet been demonstrated to imply superior clinical efficacy. Nevertheless, mucosal afferent signaling pathways are therapeutically interesting targets that should be further explored.

Treatment of the overactive bladder syndrome with muscarinic receptor antagonists - a matter of metabolites?

Antagonists of muscarinic acetylcholine receptors, such as darifenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium, are the mainstay of the treatment of the overactive bladder syndrome. Fesoterodine is a newer drug awaiting regulatory approval. We briefly review the pharmacological activity of their metabolites and discuss how active metabolites may contribute to their efficacy and tolerability in vivo. Except for trospium, and perhaps solifenacin, all of the above drugs form active metabolites, and their presence and activity need to be taken into consideration when elucidating relationships between pharmacokinetics and pharmacodynamics of these drugs. Moreover, the ratios between parent compounds and metabolites may differ depending on genotype of the metabolizing enzymes, concomitant medication, and/or drug formulation. Differential generation of active metabolites of darifenacin or tolterodine are unlikely to influence the overall clinical profile of these drugs in a major way because the active metabolites exhibit a similar pharmacological profile as the parent compound. In contrast, metabolites of oxybutynin and propiverine may behave quantitatively or even qualitatively differently from their parent compounds and this may have an impact on the overall clinical profile of these drugs. We conclude that more comprehensive studies of drug metabolites are required for an improved understanding of their clinical effects.