Prostatic relaxation induced by agmatine is decreased in spontaneously hypertensive rats

Authors

  • Liang-Ming Lee,

    1. Department of Urology, College of Medicine, Taipei Medical University–Wan-Fang Hospital, Wang-Fang, Taipei City
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    • L-M Lee and T-C Tsai contributed equally as first authors.

  • Tsung-Chin Tsai,

    1. Department of Surgery, Chi-Mei Medical Centre Liouying, Liou-Ying
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    • L-M Lee and T-C Tsai contributed equally as first authors.

  • Hsien-Hui Chung,

    1. Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University
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  • Yat-Ching Tong,

    Corresponding author
    1. Department of Urology, College of Medicine, National Cheng Kung University, Tainan City
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  • Juei-Tang Cheng

    Corresponding author
    1. Department of Surgery, Chi-Mei Medical Centre Liouying, Liou-Ying
    2. Department of Medical Research, Chi-Mei Medical Centre, Yong Kang, Tainan City, Taiwan
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Juei-Tang Cheng and Yat-Ching Tong, Department of Medical Research, Chi-Mei Medical Centre, Yong Kang, Tainan City 71101, Taiwan. e-mail: m980103@mail.chimei.org.tw

Abstract

What's known on the subject? and What does the study add?

Neurotransmitters are known to control prostate contractility. Agmatine is one of them and induces relaxation through imidazoline receptors.

The paper shows that the action of agmatine is reduced in hypertensive rats, and that this change is related to the decrease of ATP-sensitive potassium channels in the prostate. The findings can increase our understanding of the possible underlying mechanism for the development of clinical benign prostatic hyperplasia.

OBJECTIVES

  • • To compare agmatine-induced prostatic relaxation in hypertensive and control rats.
  • • To investigate the responsible mechanism(s) and the role of the ATP-sensitive potassium channel.

METHODS

  • • Prostate strips were isolated from male spontaneously hypertensive (SH) rats and normal Wistar-Kyoto (WKY) rats for measurement of isometric tension. The strips were precontracted with 1 µmol/L phenylephrine or 50 mmol/L KCl. Dose-dependent relaxation of the prostatic strips was studied by cumulative administration of agmatine, 1 to 100 µmol/L, into the organ bath.
  • • Effects of specific antagonists on agmatine-induced relaxation were studied.
  • • Western blotting analysis was used to measure the gene expression of the ATP-sensitive potassium channel in the rat prostate.

RESULTS

  • • Prostatic relaxation induced by agmatine was markedly reduced in SH rats compared with WKY rats.
  • • The relaxation caused by agmatine was abolished by BU224, a selective imidazoline I2-receptor antagonist, but was not modified by efaroxan at a dose sufficient to block imidazoline I1-receptors.
  • • The relaxation induced by diazoxide at a concentration sufficient to activate ATP-sensitive potassium channels was markedly reduced in the SH rat prostate.
  • • Expressions of ATP-sensitive potassium channel sulphonylurea receptor and inwardly rectifying potassium channel (Kir) 6.2 subunits were both decreased in the prostate of SH rats.

CONCLUSION

  • • The decrease of agmatine-induced prostatic relaxation in SH rats is related to the change in ATP-sensitive potassium channels.

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