Age dependent response to exogenous estrogen on micturition, contractility and cholinergic receptors of the rat bladder.

The age related effects of 17beta-estradiol (E) supplementation on micturition and contractility of ovariectomized rats (OVX) were evaluated. Studies were carried out in young, 2 month, and mature, 10 month old rats which were distributed into three groups: Sham-operated (SHAM), (OVX), and (OVX+E). Following treatment, urodynamic studies were performed followed by an in vitro bladder tissue evaluation. Urodynamic studies show age and time related changes in bladder function. The in vitro results show that the hormone deprived tissues of 2 months old rats had a decreased responsiveness to cholinergic stimulation; maximum contractile force occurred at 78% and 187% for the SHAM. The response from the OVX+E tissues was evident at 113%. E supplementation of the mature rats increased bladder contractile force to the same levels as SHAM (156% and 176%). The response of the mature OVX rats remained significantly below that of SHAM or OVX+E rats. Findings suggest that the impact of E on bladder function depends on age at which it is given. Differential response between young and mature to exogenous E indicates that endogenous estrogen plays a major role in the neuromuscular development of normal bladder function and micturition reflexes. Contractility data show that OVX in young rats irreversibly decreases the response of the bladder to cholinergic stimulation, suggesting that exogenous E partially restores function while in mature rats, exogenous E was able to reverse the effects of OVX.