Acquisition of Hormone‐Mediated Mechanisms Regulating Testicular Steroidogenesis during Development

Abstract

Our studies have demonstrated that in the fetal rat Leydig cell, estradiol causes an up-regulation of its receptor and an induction of the regulatory mechanism (late steroidogenic lesion) that is similar to that observed in the adult rat Leydig cell. The absence of this regulation in fetal life is due to a very low level of aromatization capacity, with lack of up-regulation and/or induction of estrogen receptor by estradiol. Higher doses or frequent administration of LH is able to elevate aromatase activity and consequent E2-receptor-mediated action for the induction of gonadotropin-mediated desensitization in fetal cells. Our studies have revealed a small population of adult-like Leydig cells in the fetal testis and the emergence of a functional adult-like population from the fetal Leydig cell induced by gonadotropin treatment. The in vitro fetal Leydig cell culture system has permitted the analysis of cellular actions of gonadotropin with particular reference to the role of tropic hormone and estrogen in the development of late steroidogenic lesions during Leydig cell maturation. Future research with this system will help to clarify further the modulatory mechanisms responsible for emergence of the adult cell population.

Estrogens in males: what have we learned in the last 10 years?

“…The development of testicular paracrinology between 1980s and 1990s played a significant role in the study of estrogens in the male reproductive function [17][18][19]: the interest in understanding in detail the regulatory role of each paracrine substance in the complicated hormonal network in the testicular milieu, as well as the "mystery" of cell-to-cell interaction in the testis, provided strong stimuli to researchers. In this view, starting from biochemical studies on aromatization of androgens to estrogens [20][21][22][23][24][25][26][27][28][29], the following immunocytochemical studies on both aromatase [30][31][32][33] and estrogen receptors (ER) [34][35][36][37][38][39] directed the interest of biologists to the significance of estrogens signaling the pathway in the male reproductive system. Progress in molecular biology leaded to gene cloning for aromatase [40][41][42], ERα [43][44][45] and ERβ [46][47][48] gene cloning, this being a crucial step for the following deep investigation of estrogens physiology in the male.…”

Estrogen in the adult male reproductive tract: A review

“…Most interesting was the discovery that cytochrome P450 aromatase, which is capable of converting androgens into estrogens, is present in the testis [25-39]. During this same period of discovery, others were using the radioimmunoassay to identify steroids present in body fluids and estrogen concentrations were found to be relatively high in seminal and rete testis plasma [40-48].…”

Developmental Pattern of 17β-Hydroxysteroid Dehydrogenase and 5α-Reductase Activities in the Foreskin of Boys from Birth to Eight Years of Age

“…26]. In the testis, hor mone-mediated mechanisms regulating testicular ste roidogenesis during development probably involve es trogens produced locally by testicular aromatase [26]. Whether similar mechanisms are also involved in the regulation of genital skin enzymes is not known.…”