We sought to investigate the influence of 17beta-estradiol (E-2) on key enzymes of lipogenesis and lipolysis in subcutaneous (SC) abdominal adipocytes isolated from women. In addition, we wished to determine the influence of an anti-estrogen, ICI: compound 182,780 (anti-E), known to act via the estrogen receptor (ER), alone and in combination with E-2. Adipose tissue was obtained from 17 women undergoing elective surgery, with a mean age of 47 years (range, 34 to 62), mean weight of 65.4 kg (range, 58.1 to 75.0), and mean body mass index (BMI) of 25 kg/m(2) (range, 22 to 27). Isolated adipocytes were treated with varying doses of E-2, anti-E, or E-2 in combination with anti-E 10(-8) mol/L for 48 hours. Following treatment, proteins were extracted and the effects on lipogenesis and lipolysis were assessed, using Western blotting to determine the relative expression of the key enzymes of these processes, lipoprotein lipase (LPL; 56 kd), and hormone-sensitive lipase (HSL; 84 kd), respectively. Glycerol release into the medium was also measured as an index of lipolytic activity. The protein expression studies demonstrated that E-2 altered expression of LPL relative to control, with the highest dose significantly reducing LPL expression and the lower doses significantly increasing LPL expression (mean protein expression relative to control +/- SE): E-2 10(-12) mol/L, 1.79 +/- 0.16 (P <.001); E-2 10(-7) mol/L, 0.56 +/- 0.08 (P <.05). In contrast, HSL expression was increased relative to control at the higher doses of E-2 but was not significantly altered relative to control at the lower doses: E-2 10(-12) mol/L, 1.02 +/- 0.14 (P > .05); E-2 10(-7) mol/L, 1.55 +/- 0.17 (P <.01). Anti-E 10(-8) mol/L alone reduced LPL protein expression relative to control (P <.05) and increased HSL protein expression relative to control (P > .05). In combination with E-2 10(-7) mol/L, anti-E 10(-8) mol/L did not abrogate the inhibitory effect on LPL expression relative to control (P <.05). Furthermore, E-2 10(-7) mol/Lin combination with anti-E 10(-8) mol/L, displayed a stimulatory effect on HSL expression relative to control (P <.01). Glycerol release studies following the higher doses of E-2, and also following E-2 10(-7) mol/L in combination with anti-E 10(-8) mol/L, provided support for the HSL protein expression studies. We conclude that the highest concentration of E-2 (10(-7) mol/L) significantly reduced LPL expression relative to control, while the lower concentrations significantly increased LPL expression relative to control. The highest concentration of E-2 also significantly increased both HSL expression and glycerol release relative to control. The effects of anti-E suggest that the in vitro effects of E-2 on lipogenesis and lipolysis occur, at least in part, through a receptor-mediated pathway. In addition, as recently observed in other tissues, ICI:compound 182,780 does not appear to behave as a pure anti-estrogen in isolated human adipocytes. Copyright 2003 Elsevier, Inc. All rights reserved.