Production of endothelin by canine prostatic epithelial cells and its stimulatory effects on their growth

The current study has been designed to explore expressions of endothelin (ET) receptors and ETs in the canine prostate and the effect of ETs on canine prostatic epithelial cells. ET receptors were characterized by biotinylated ET-1 binding in frozen sections of the prostate. Canine prostatic epithelial cells in primary culture were used for demonstration of ET-1 expression by reverse-phase HPLC coupled with radioimmunoassay and Northern blotting and were subjected to growth assay. Biotinylated ET-1 binding was localized in the epithelial component, and the binding was also blocked with an antagonist specific for ET(B) subtype receptors. ET-1 and ET-3 stimulated canine prostatic epithelial cell growth in vitro. The effect was also reversed in the presence of an antagonist specific for ET(B) subtype receptors. Elution profile of epithelial cell culture medium revealed two peaks, corresponding to ET-1 and big ET-1. Epithelial cells in culture expressed pre-pro-ET-1 mRNA. Canine prostatic epithelial cells expressed ET(B) receptors and ET-1. It appears most likely that the expressed ET-1 acts as an autocrine/paracrine proliferative factor on canine prostatic epithelial cells via ET(B) receptors.