ANDROGEN RECEPTORS IN CULTURED RAT ADIPOSE PRECURSOR CELLS DURING PROLIFERATION AND DIFFERENTIATION - REGIONAL SPECIFICITIES AND REGULATION BY TESTOSTERONE

Different studies suggest that sex hormones affect adipose tissue metabolism and deposition. To investigate the possibility that androgens may play a role in adipose tissue development, we have studied androgen receptors (AR) in rat adipose precursor cells from two different anatomical fat deposits, one deep intraabdominal (epididymal) and one subcutaneous (inguinal) during the proliferation and differentiation processes. AR were quantified by [H-3]R1881 specific binding in whole cells and the nuclear fraction and were localized by immunocytofluorimetry in both the cytosol and the nucleus. During the proliferative phase, total AR level decreased from D3 to D6. At confluence (D5), AR were higher in epididymal (64+/-4 fmol/mg protein) than in subcutaneous (33+/-3 fmoles/mg proteins) preadipocytes and were up-regulated by testosterone but not by 5 alpha-dihydrotestosterone or by 17 beta-estradiol. At differentiation (D1011), nuclear AR decreased by 50% in both precursor fat cell populations when compared to the confluent state (D5) and AR were no more up-regulated but rather down-regulated by testosterone. Because AR are present in preadipocytes and are differently regulated by testosterone depending on the stage of proliferation and differentiation, this study suggests that testosterone may play a role in the control of the adipogenic process.