Assessment and Characterization of Purinergic Contractions and Relaxations in the Rat Urinary Bladder

Abstract

The aim of the present study was to assess the purinoceptor functional responses of the urinary bladder by using isolated rat urinary bladder strip preparations. ATP elicited a transient bladder contraction followed by a sustained relaxation and ADP, UDP and UTP generated predominantly potent relaxations (relaxatory potencies: ADP = ATP > UDP = UTP). The ATP contractions were desensitized with the P2X 1 ⁄ 3 purinoceptor agonist ⁄ desensitizer a,b-meATP and reduced by the P2 purinoceptor antagonist PPADS but unaffected by the P2 purinoceptor antagonist suramin. Electrical field stimulation (1-60 Hz) evoked frequency-dependent bladder contractions that were decreased by incubation with a,b-meATP but not further decreased by PPADS. Suramin antagonized relaxations generated by UDP but not those by ADP, ATP or UTP. PPADS antagonized and tended to antagonize UTP and UDP relaxations, respectively, but did neither affect ADP nor ATP relaxations. ADP relaxations were insensitive to the P2Y 1 purinoceptor antagonist MRS 2179 and the ATP-sensitive potassium channel antagonist glibenclamide. The ATP relaxations were inhibited by the P1 purinoceptor antagonist 8-p-sulfophenyltheophylline but unaffected by the A2A adenosine receptor antagonist 8-(3-chlorostyryl)caffeine and glibenclamide. Adenosine evoked relaxations that were antagonized by the A2B adenosine receptor antagonist PSB 1115. Thus, in the rat urinary bladder purinergic contractions are elicited predominantly by stimulation of the P2X 1 purinoceptors, while UDP ⁄ UTP-sensitive P2Y purinoceptor(s) and P1 purinoceptors of the A2B adenosine receptor subtype are involved in bladder relaxation.The contraction of the urinary bladder depends mainly on the parasympathetic stimulation of the muscarinic receptors populating the detrusor [1]. However, as early as 1895 Langley described that a certain part of the contractile response of the bladder is resistant to atropine [2]. It was later suggested that other transmitters besides acetylcholine and noradrenaline contribute to the regulation of the urinary bladder function, and adenosine-5¢-triphosphate (ATP) was identified as one of these transmitters [3]. ATP generates a transient contraction caused by the stimulation of the P2X purinoceptors causing depolarization through non-selective cation channels [4]. Of the seven known homomeric P2X purinoceptor subtypes, the P2X 1 subtype has been shown to occur in the smooth muscle of the rat bladder [5]. It has also been demonstrated that the P2X 1 subtype is the predominant purinoceptor present in the human bladder [6]. Following the ATP-generated contraction, a sustained relaxation occurs, which has been suggested to depend on the metabolite of ATP, adenosine, stimulating inhibitory P1 purinoceptors [3,7]. Others have attributed the relaxation to the direct action of ATP at G-protein-coupled P2Y purinoceptors [8,9].The present study was undertaken to further investigate and characterize the functional responses of the purinoceptors in the normal rat urinary bladder. Th...

Pharmacological characterization of uracil nucleotide-preferring P2Y receptors modulating intestinal motility: a study on mouse ileum

“…Contractions Fig. 4 Original tracings showing the effects on the spontaneous mechanical activity of the longitudinal muscle of a mouse ileum induced by the P2Y 2 , P2Y 2 / 4 , and P2Y 6 receptor agonists, 2-thio-UTP, UTPγS, and PSB 0474 (10 μM each), respectively generated by UTP and UDP in ileum muscle are identical, indicating that the tissue responds similarly to UTP and UDP, as reported in rat mesenteric and basilar arteries [26,27] or in rat urinary bladder [28].…”

The effect of hypercholesterolemia on the contractions of detrusor strips in response to neural stimulation in rats

“…α,β-meATP, an ATP analog, is a selective P2X receptor agonist and resistant to ATPase. Thus, repeated application of α,β-meATP can desensitize the P2X receptors (24,25). In the present study, the purinergic component was found to be as ~30% (field stimulation at 10 Hz) in the presence of PPADS and ~33% (field stimulation at 10 and 20 Hz) in response to desensitization with α,β-meATP both in the NC and the HC group out of ~60% atropine-resistant contractions.…”

“…P2X receptors (mainly P2X 1 ), expressed in mammalian bladders, are ATP-gated ion channels that contribute to urinary bladder functions (24,28). Several studies suggested that PPADS strongly suppresses P2X-purinoceptor-mediated contractions (25,31,32). α,β-meATP, an ATP analog, is a selective P2X receptor agonist and resistant to ATPase.…”

“…In the third protocol, either P2X antagonist phosphate-6-azo (benzene-2,4-disulfonic acid) tetrasodium salt hydrate (PPADS) (10 -4 M) (24) or P2X agonist α,β-methylene-adenosine-5'-triphosphate (α,β-meATP) (10 -5 M) (25) was added to the bath in the presence of atropine (10 -6 M) to isolate the noncholinergic component of the parasympathetic stimulation. EFS was repeated after an incubation period of 40 min for PPADS.…”

Nicotine interferes with purinergic signaling in smooth muscle cells isolated from urinary bladders of patients with lower urinary tract symptoms

“…ACh and ATP stimulate muscarinic and purinergic receptors of the smooth muscle, respectively, and elicit bladder contraction (Dowdall et al 1974;Kasakov and Burnstock 1982;Theobald and de Groat 1989). Although ATP plays an additional role in evoking the contraction of the detrusor in many species (rabbit, rat, mice;Calvert et al 2001;Aronsson et al 2010;Gomez-Pinilla et al 2011), it has little, if any, role in healthy human bladders (Sjogren et al 1982;Bayliss et al 1999). On the other hand, the proportion of atropine-resistant, nerve-mediated contractions in human bladders increases in several pathological conditions (interstitial cystitis, idiopathic detrusor overactivity, etc.…”