Expression of 5-Hydroxytryptamine Receptors in Human Urinary Bladders with Benign Prostatic Hyperplasia

Introduction This study investigated the mRNA expression pattern and distribution of 5-hydroxytryptamine (5-HT) receptors 5-HT 2A , 5-HT 2B , 5-HT 3A , 5-HT 4 , and 5-HT 7 within the urothelium and detrusor of normal bladder tissue and in the urothelium of bladders from patients with benign prostatic hyperplasia (BPH). Methods Normal urinary bladder specimens were obtained from 13 patients undergoing radical cystectomy due to bladder cancer (normal group) and BPH specimens were obtained from 27 benign prostatic obstruction patients receiving transurethral prostatectomy or retropubic prostatectomy. Receptor subtype mRNA expression was determined by real-time reverse transcription polymerase chain reaction on urothelium, detrusor, and whole mucosal preparations. Receptor distribution was determined by immunohistochemistry. Results In normal tissues, expressions of 5-HT 2B and 5-HT 7 receptor mRNAs in the urothelium, detrusor, and whole mucosa were greater than the average expression for all receptor subtype mRNAs. 5-HT 2B receptor protein was distributed in the apical urothelium and among the detrusor smooth muscle layers. In contrast, the 5-HT 7 receptors were within the urothelium middle cell layers and detrusor smooth muscle cells. The expression pattern of each 5-HT receptor subtype mRNA within the BPH urothelium was similar to that in the normal urothelium. The expression level of 5-HT 2A receptor mRNA in the BPH group was significantly lower than the normal group; however, the expressions of both 5-HT 3A and 5-HT 7 mRNAs were significantly higher. The expressions of both 5-HT 2B and 5-HT 4 mRNAs were not significantly different between the normal and BPH groups. Conclusion In normal urinary bladders, the expressions of both 5-HT 2B and 5-HT 7 mRNAs were higher compared to the 5-HT 2A , 5-HT 3A , and 5-HT 4 mRNAs. The distributions of 5-HT 2B and 5-HT 7 receptors were different in the urothelium and detrusor layers. The 5-HT 3A and 5-HT 7 receptor mRNAs in the BPH group were significantly higher compared to the normal urothelium, while the 5-HT 2A mRNA was significantly lower. Funding Asahi Kasei Pharma Corporation.