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Melatonin restores impaired contractility in aged guinea pig urinary bladder

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Author

Summary, in English

Urinary bladder disturbances are frequent in the elderly population but the responsible mechanisms are poorly understood. This study evaluates the effects of aging on detrusor myogenic contractile responses and the impact of melatonin treatment. The contractility of bladder strips from adult, aged and melatonin-treated guinea pigs was evaluated by isometric tension recordings. Cytoplasmatic calcium concentration ([Ca2+](i)) was estimated by epifluorescence microscopy of fura-2-loaded isolated detrusor smooth muscle cells, and the levels of protein expression and phosphorylation were quantitated by Western blotting. Aging impairs the contractile response of detrusor strips to cholinergic and purinergic agonists and to membrane depolarization. The impaired contractility correlates with increased [Ca2+](i) in response to the stimuli, suggesting a reduced Ca(2+)sensitivity. Indeed, the agonist-induced contractions in adult strips were sensitive to blockade with Y27362, an inhibitor of Rho kinase (ROCK) and GF109203X, an inhibitor of protein kinase C (PKC), but these inhibitors had negligible effects in aged strips. The reduced Ca2+ sensitivity in aged tissues correlated with lower levels of RhoA, ROCK, PKC and the two effectors CPI-17 and MYPT1, and with the absence of CPI-17 and MYPT1 phosphorylation in response to agonists. Interestingly, melatonin treatment restored impaired contractility via normalization of Ca2+ handling and Ca2+ sensitizations pathways. Moreover, the indoleamine restored age-induced changes in oxidative stress and mitochondrial polarity. These results suggest that melatonin might be a novel therapeutic tool to palliate aging-related urinary bladder contractile impairment.

Publishing year

2008

Language

English

Pages

416-425

Publication/Series

Journal of Pineal Research

Volume

44

Issue

4

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Pharmacology and Toxicology
  • Physiology
  • Medicinal Chemistry

Keywords

  • melatonin
  • guinea pig
  • calcium signalling
  • aging
  • calcium sensitization
  • mitochondria
  • urinary bladder

Status

Published

Research group

  • Vascular Physiology

ISBN/ISSN/Other

  • ISSN: 1600-079X