Expression of prostaglandin E₂ receptor subtypes in the canine lower urinary tract varies according to the gonadal status and gender

Abstract

Locally-synthesised prostaglandin E₂ (PGE₂) is pivotal for the function of the lower urinary tract (LUT). This study aimed at investigating the expression and distribution pattern of the four PGE₂ receptor (EP) subtypes in the LUT of intact and gonadectomised male and female dogs. Expression for EP1, EP2, EP3, and EP4 and their mRNA (EP2, EP3, and EP4) was investigated. Twenty clinically healthy dogs were allotted into 4 groups based on their gonadal status and gender including 5 intact males, 5 anoestrous females, 4 castrated males, and 6 spayed females. In situ hybridization and immunohistochemistry showed variation in the expression of mRNA and protein for the EP subtypes among tissue layers (epithelium, sub-epithelial stroma, and muscle), regions (body and neck of the bladder as well as proximal and distal urethra) and between gonadal statuses and genders. The expression for the four EPs was intense in the luminal epithelium, intermediate to low in the muscle and the sub-epithelial stroma regardless of gonadal status or gender. Higher expression of all EPs and their mRNAs was observed in the proximal urethra compared to other regions in intact dogs. However, in gonadectomised dogs, the expression did not differ among different regions and was generally lower than in intact dogs particularly in the proximal urethra. Differences in the expression between genders were found and depended on EP subtypes. In conclusion, the results have shown that four subtypes of EP receptors and their mRNAs are present in the canine LUT and their expression was affected by the gonadal status and the gender. The results lead to suggest that an impaired LUT function post-neutering may partly be associated with differences in PGE₂ receptor expression between intact and gonadectomised dogs.