Estrogen and Postnatal Maturation Increase Caveolar Number and Caveolin-1 Protein in Bladder Smooth Muscle Cells

ABSTRACTPurpose: Clinical studies indicate that detrusor contractility decreases in old age and the dense band pattern with caveolar depletion represents the ultrastructural norm of the aged human detrusor. We performed animal studies to explore the hypothesis that lowering estrogen induces the dense band pattern with estrogen replacement restoring usual sarcolemmal appearance and increasing caveolar number.Materials and Methods: Newborn, young (1-month-old) and middle-aged (13 to 14-month-old) female rats were studied. Middle-aged animals were evaluated 4 months after sham operation or ovariectomy (OVx) with OVx rats receiving placebo or 25% 17β-estradiol (E2) capsules for 1 week prior to sacrifice. Electron microscopy was used to evaluate sarcolemmal structure and quantify caveolar numbers in bladder muscle cells. Caveolae were also assessed by measuring caveolin-1 protein.Results: Alternating electron dense and thinner zones with abundant caveolae were present in bladder sarcolemma from middle-aged ani...