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Decreased contractile effect of endothelin-1 on hyperplastic prostate
N Moriyama1, S Kurimoto, N Miyata
1Department of Urology, Faculty of Medicine, University of Tokyo, Japan.
General Pharmacology
|September 1, 1996
Summary
Endothelin-1 (ET-1) causes prostate contraction, but this effect is reduced in benign prostatic hyperplasia (BPH). Despite increased ET-1 receptors in BPH, their distribution limits contractile regulation, suggesting ET-1 is not key to BPH symptoms.
Area of Science:
- Urology
- Endocrinology
- Molecular Biology
Background:
- Endothelin-1 (ET-1) is a potent vasoconstrictor involved in various physiological processes.
- Benign prostatic hyperplasia (BPH) is a common condition in aging men characterized by prostate enlargement.
- The role of ET-1 in the pathophysiology of BPH remains incompletely understood.
Purpose of the Study:
- To investigate the contractile activity, binding characteristics, and localization of ET-1 in human nonhyperplastic (control) and hyperplastic prostates.
- To determine the functional significance of ET-1 and its receptors in the context of BPH.
Main Methods:
- Comparative analysis of prostate tissue from control and BPH subjects.
- Assessment of ET-1-induced contractile responses in isolated prostate tissues.
- Quantification of ET-1 receptor binding using Bmax and Kd values.
- Immunohistochemical staining for ET-1 localization within prostate tissues.
Main Results:
- ET-1 induced dose-dependent contractions in both control and hyperplastic prostates, but the response was significantly diminished in hyperplastic tissues.
- Hyperplastic prostates exhibited increased maximal binding (Bmax) and dissociation constant (Kd) values for ET-1 receptors compared to controls.
- Strong ET-1 staining was observed in the muscle and proliferative epithelium of hyperplastic prostates, contrasting with weak staining in the glandular epithelium of control prostates.
Conclusions:
- Despite increased ET-1 and ET-1 receptor expression in BPH, the responsiveness to ET-1 is decreased.
- The altered distribution of ET-1 receptors, particularly their dominance in the proliferated gland, may impair their ability to regulate contractile responses.
- These findings suggest that ET-1 may not play a significant role in mediating the obstructive symptoms associated with benign prostatic hyperplasia.