Effects of endogenous ovarian estrogen versus exogenous estrogen replacement on blood flow and ERα and ERβ levels in the bladder

Objective. Determine the effect of endogenous estrogen versus estrogen replacement therapy (ERT) on bladder blood flow (BBF) and estrogen receptors (ERs). Methods. BBF was determined with radiolabeled microspheres in luteal, follicular, pregnant, oophorectomized (Ovx) sheep, and Ovx sheep with ERT. Estrogen receptors (ERα, ERβ) were quantified using Western blot analysis. Results. Compared to luteal and follicular ewes, BBF was reduced in pregnancy and following oophorectomy. Estrogen replacement therapy in Ovx sheep restored BBF to luteal levels. Estrogen receptor-α predominated, whereas ERβ was not detectable. Estrogen receptor-α levels were unaffected by the ovarian cycle and increased in pregnancy, as well as in Ovx sheep with and without chronic ERT. Conclusion. The combination of diminished BBF and elevated ERα levels in both pregnant and Ovx sheep suggests an inverse relationship between BBF and ERα in the bladder. Although chronic ERT in Ovx sheep restored BBF, it did not restore ERα back to luteal levels.