Regulatory effect of castration on endothelins, their receptors and endothelin‐converting enzyme in rat seminal vesicle

OBJECTIVE To investigate the effects of castration on the expression of endothelins (ETs), ET receptors and ET converting enzyme‐1 (ECE‐1) in the rat seminal vesicle (RSV). MATERIALS AND METHODS Sprague‐Dawley rats (3 months old) were surgically castrated or sham‐operated, and then killed 7 days after surgery. Biochemical and pharmacological properties and the location of ET receptors in the RSV were determined by a series of binding experiments with [125I]ET‐1, using membrane particulates and slide‐mounted frozen sections of RSV. Expression levels of ETA and ETB receptor subtypes, ET‐1, ET‐3 and ECE‐1 mRNAs were assessed by relative multiplex reverse‐transcription polymerase chain reaction (RT‐PCR). RESULTS The density of total ET receptors increased significantly in the seminal vesicle of the castrated rat. The predominance of the ETA receptor subtype in the RSV did not change with castration. Autoradiographic studies showed the presence of ET receptors on the smooth muscle and epithelium of the RSV. In addition, RT‐PCR showed an up‐regulation in the expression of ETA and ETB receptor subtypes, ET‐1 and ECE‐1 mRNAs in the seminal vesicle of the castrated rat. However, castration caused no significant change in the expression levels of ET‐3 mRNA. CONCLUSION These findings suggest a regulatory role for testosterone in the expression of the ET receptor system in the RSV.