Reducing endogenous estrogen during development alters hormone production by porcine Leydig cells and seminiferous tubules

High levels of estrogen produced by boar testes and the presence of estrogen receptors in both interstitial and tubular compartments are consistent with a direct role for estrogen in regulation of testicular cell function. This study investigated the importance of estrogen on hormone production by Leydig cells and seminiferous tubules in the developing boar. Thirty-six I-week-old littermate pairs of boars were treated weekly with vehicle or 0.1 mg/kg BW Letrozole, an aromatase inhibitor, until castration at 2, 3, 4, 5, 6, 7, or 8 months. Tissue was collected and Leydig cells and seminiferous tubules were isolated. In a separate study, five untreated boars (ages 1.5-4 months) were castrated and Letrozole was added in vitro to Leydig cell and seminiferous tubule cultures. Leydig cells were cultured for 24 h with and without porcine LH. Media were assayed for estradiol (E-2) and testosterone (T) concentrations by RIA. Seminiferous tubules were cultured for 4 h with and without porcine FSH; media were assayed for E2 and immunoreactive inhibin (INH). In vivo aromatase inhibition decreased basal E2 and increased basal T production by cultured Leydig cells. Basal seminiferous tubule production of E2 but not INH was reduced. Decreasing estrogen synthesis in vivo did not alter LH-induced Leydig cell E2 production or FSH-induced seminiferous tubule INH production. INH production decreased with advancing age regardless of treatment. In conclusion, in vivo aromatase inhibition altered baseline steroid production by cultured Leydig cells and seminiferous tubules but had little effect on response to gonadotropins. (c) 2007 Published by Elsevier Inc.