Dataset Information

Functional, morphological and molecular characterization of bladder dysfunction in streptozotocin-induced diabetic mice: evidence of a role for L-type voltage-operated Ca2+ channels.

ABSTRACT:

Background and purpose

Diabetic cystopathy is one of the most common and incapacitating complications of diabetes mellitus. This study aimed to evaluate the functional, structural and molecular alterations of detrusor smooth muscle (DSM) in streptozotocin-induced diabetic mice, focusing on the contribution of Ca(2+) influx through L-type voltage-operated Ca(2+) channels (L-VOCC).

Experimental approach

Male C57BL/6 mice were injected with streptozotocin (125?mg·kg(-1) ). Four weeks later, contractile responses to carbachol, ?,?-methylene ATP, KCl, extracellular Ca(2+) and electrical-field stimulation were measured in urothelium-intact DSM strips. Cystometry and histomorphometry were performed, and mRNA expression for muscarinic M(2) /M(3) receptors, purine P2X1 receptors and L-VOCC in the bladder was determined.

Key results

Diabetic mice exhibited higher bladder capacity, frequency, non-void contractions and post-void pressure. Increased bladder weight, wall thickness, bladder volume and neural tissue were observed in diabetic bladders. Carbachol, ?,?-methylene ATP, KCl, extracellular Ca(2+) and electrical-field stimulation all produced greater DSM contractions in diabetic mice. The L-VOCC blocker nifedipine almost completely reversed the enhanced DSM contractions in bladders from diabetic animals. The Rho-kinase inhibitor Y27632 had no effect on the enhanced carbachol contractions in the diabetic group. Expression of mRNA for muscarinic M(3) receptors and L-VOCC were greater in the bladders of diabetic mice, whereas levels of M(2) and P2X1 receptors remained unchanged.

Conclusions and implications

Diabetic mice exhibit features of urinary bladder dysfunction, as characterized by overactive DSM and decreased voiding efficiency. Functional and molecular data suggest that overactive DSM in diabetes is the result of enhanced extracellular Ca(2+) influx through L-VOCC.

SUBMITTER: Leiria LO

PROVIDER: S-EPMC3144540 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Publications

Functional, morphological and molecular characterization of bladder dysfunction in streptozotocin-induced diabetic mice: evidence of a role for L-type voltage-operated Ca2+ channels.

Leiria L O S LO Mónica F Z T FZ Carvalho F D G F FD Claudino M A MA Franco-Penteado C F CF Schenka A A Grant A D AD De Nucci G G Antunes E E

British journal of pharmacology 20110701 6

<h4>Background and purpose</h4>Diabetic cystopathy is one of the most common and incapacitating complications of diabetes mellitus. This study aimed to evaluate the functional, structural and molecular alterations of detrusor smooth muscle (DSM) in streptozotocin-induced diabetic mice, focusing on the contribution of Ca(2+) influx through L-type voltage-operated Ca(2+) channels (L-VOCC).<h4>Experimental approach</h4>Male C57BL/6 mice were injected with streptozotocin (125 mg·kg(-1) ). Four weeks ...[more]

PMID: 21391978

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Project description:Voltage-dependent Na+ channel activation underlies action potential generation fundamental to cellular excitability. In skeletal and cardiac muscle this triggers contraction via ryanodine-receptor (RyR)-mediated sarcoplasmic reticular (SR) Ca2+ release. We here review potential feedback actions of intracellular [Ca2+] ([Ca2+]i) on Na+ channel activity, surveying their structural, genetic and cellular and functional implications, translating these to their possible clinical importance. In addition to phosphorylation sites, both Nav1.4 and Nav1.5 possess potentially regulatory binding sites for Ca2+ and/or the Ca2+-sensor calmodulin in their inactivating III-IV linker and C-terminal domains (CTD), where mutations are associated with a range of skeletal and cardiac muscle diseases. We summarize in vitro cell-attached patch clamp studies reporting correspondingly diverse, direct and indirect, Ca2+ effects upon maximal Nav1.4 and Nav1.5 currents (Imax) and their half-maximal voltages (V1/2) characterizing channel gating, in cellular expression systems and isolated myocytes. Interventions increasing cytoplasmic [Ca2+]i down-regulated Imax leaving V1/2 constant in native loose patch clamped, wild-type murine skeletal and cardiac myocytes. They correspondingly reduced action potential upstroke rates and conduction velocities, causing pro-arrhythmic effects in intact perfused hearts. Genetically modified murine RyR2-P2328S hearts modelling catecholaminergic polymorphic ventricular tachycardia (CPVT), recapitulated clinical ventricular and atrial pro-arrhythmic phenotypes following catecholaminergic challenge. These accompanied reductions in action potential conduction velocities. The latter were reversed by flecainide at RyR-blocking concentrations specifically in RyR2-P2328S as opposed to wild-type hearts, suggesting a basis for its recent therapeutic application in CPVT. We finally explore the relevance of these mechanisms in further genetic paradigms for commoner metabolic and structural cardiac disease.

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Dataset Information

Functional, morphological and molecular characterization of bladder dysfunction in streptozotocin-induced diabetic mice: evidence of a role for L-type voltage-operated Ca2+ channels.

Background and purpose

Experimental approach

Key results

Conclusions and implications

Publications

Functional, morphological and molecular characterization of bladder dysfunction in streptozotocin-induced diabetic mice: evidence of a role for L-type voltage-operated Ca2+ channels.

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