This Article Full Text Full Text (PDF) All Versions of this Article: 30/5/590    most recent Author Manuscript (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Oliveira, C. A. Articles by Hess, R. A. PubMed PubMed Citation Articles by Oliveira, C. A. Articles by Hess, R. A.

Cellular and Regional Distributions of Ubiquitin-Proteasome and Endocytotic Pathway Components in the Epithelium of Rat Efferent Ductules and Initial Segment of the Epididymis

REX A. HESS

From the ^* Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil; and the Department of Veterinary Biosciences, University of Illinois, Urbana, Illinois.

Correspondence to: Dr Rex A. Hess, Department of Veterinary Biosciences, University of Illinois, 2001 S Lincoln, Urbana, IL 61802-6199 (e-mail: rexhess{at}illinois.edu).

Abstract

Efferent ductules of the male reproductive tract contain high concentrations of estrogen receptors (ER), which are essential for the regulation of fluid reabsorption and maintenance of normal epithelial morphology. Treatments with the antiestrogen ICI 182,780 and 17β-estradiol cause a reduction in ER expression; however, the mechanisms governing the down-regulation are undetermined. In other tissues, the ubiquitin-proteasome pathway appears to have a dominant role in regulating ER turnover, although in the efferent ductules, an abundance of epithelial lysosomes could also participate in protein turnover. To study this activity, the expressions of proteasome, ubiquitin, and markers for the endocytotic apparatus (early endosome antigen-1 [EEA1], clusterin, and cathepsin D) were examined in rat efferent ductules and initial segment of epididymis. Distinct cellular, subcellular, and regional distributions of these proteins were observed in the epithelial cells. A gradient of proteasome, ubiquitin, EEA1, and clusterin staining was seen in the efferent ducts, which decreased 30%–41% from the proximal zone to the terminal common duct. Antiestrogen treatment resulted in significant decreases in proteasome, EEA1, and clusterin in the efferent ducts. Localization of ubiquitin-proteasome and endocytotic pathway components suggests that differential regulation is required for protein degradation and turnover in efferent ductules and head of the epididymis.

     Key words: Lysosome, endosome, cathepsin, ICI 182,780