ENDOTHELINS IN CANINE GENITOURINARY TISSUES

Purpose: To characterize the functional effect of endothelin-1 (ET1) a nd endothelin-3 (ET3), immunohistochemically localize ET1-like immunor eactivity, and measure the tissue levels of immunoreactive endothelin (irET) in canine genitourinary (GU) tissues. Materials and Methods: Ca nine GU tissues were characterized by measuring ET1 levels using a RIA , immunohistochemical staining of ET1 and isometric tension studies. R esults: Immunoreactive endothelin was present, to varying degrees, in the vas deferens, ureter, prostate, bladder and urethra. Functionally, ET1 demonstrated the typical concentration response characteristics i n the canine bladder base, bladder body, and prostate. The maximal ten sion (E(max)) measured following ET1 challenge was approximately 20-fo ld greater in the bladder body (0.67 +/- 0.21 g/mm.(2)) and bladder ba se (0.48 +/- 0.18 g/mm.(2)) as compared to the prostate 0.04 +/- 0.001 g/mm.(2) The E(max) of ET3 in the bladder body (0.31 +/- 0.12 g/mm.(2 )) and bladder base (0.19 +/- 0.08 g/mm.(2)) was significantly lower t han the corresponding E(max) of ET1. No measurable contractile respons e was elicited by ET3 in the canine prostate. Immunohistochemical stai ning localized the ET-like immunoreactivity to the glandular epitheliu m of the prostate and the transitional epithelium of the bladder. Conc lusions: Endothelins are ubiquitous in the canine lower GU tract with predominant localization to the epithelial elements. Endothelins are a lso functionally active in canine GU tissues, but the specific role of endothelins in the physiology and pathophysiology of GU tissues requi res further investigation.