%0 Journal Article
%T Estrogen regulation of testicular function
%A Benson T Akingbemi
%J Reproductive Biology and Endocrinology
%D 2005
%I BioMed Central
%R 10.1186/1477-7827-3-51
%X The testis consists of two compartments: seminiferous tubules and intertubular tissue, which forms the interstitium. Seminiferous tubules are lined by layers of germ cells in various stages of development (spermatogonia, spermatocytes, spermatids, spermatozoa) and supporting Sertoli cells. The interstitium consists of loose connective tissue, blood and lymphatic vessels, and various cell types, including Leydig cells, fibroblasts, macrophages and leukocytes. Leydig cells are the predominant source of the male sex steroid hormone testosterone. However, recent observations challenge the dogma that the male phenotype is maintained solely by testosterone binding to its protein target, i.e., the androgen receptor. Growing public concerns that exposures to environmental chemicals with estrogenic activity may impact human reproductive health have focused attention on the role of estrogen in male reproductive health [1]. The aromatization of C19 androgens, i.e., testosterone and androstenedione, is a key step in estrogen (E2) biosynthesis and is catalyzed by the aromatase enzyme, which is a product of the CYP19 gene [2]. The serum levels of E2 measure about 40 pg/mL in male rats [3], and ranges between 20 and 40 pg/mL in men [4]. Evidence from several studies indicates that aromatase, ER¦Á and ER¦Â are encoded by separate genes but are co-expressed with androgen receptors in the male reproductive tract [2,3]. In consonance with localization studies, mice which have targeted deletion of the aromatase gene, ER¦Á and/or ER¦Â showed altered testicular morphology and derangements of spermatogenesis [5-7], and exposures of laboratory species and wildlife to estrogenic chemicals were found to cause abnormalities of the reproductive tract [8].Although the present review is focused on direct estrogen action in the testis, estrogen regulation may occur indirectly by changes caused in the hypothalamus and pituitary. Gonadal steroids act on the hypothalamus to affect GnRH pulses, and at th
%U http://www.rbej.com/content/3/1/51